feat(app): add Simplified Chinese localization

apps/MTPLXApp/Sources/MTPLXAppHost/App/MTPLXApp.swift

@@ -318,7 +318,7 @@ struct MTPLXApp: App {
 
             CommandMenu("View") {
                 ForEach(Array(AppTab.allCases.enumerated()), id: \.element.id) { index, tab in
-                    Button(tab.title) {
+                    Button(tab.title.mtplxLocalized) {
                         router.select(tab)
                     }
                     .keyboardShortcut(KeyEquivalent(Character("\(index + 1)")), modifiers: [.command])
@@ -329,7 +329,7 @@ struct MTPLXApp: App {
                 Button("Previous Tab") { router.previousTab() }
                     .keyboardShortcut("[", modifiers: [.command])
                 Divider()
-                Button(router.benchmarkOverlayPresented ? "Close Benchmark" : "Open Benchmark") {
+                Button((router.benchmarkOverlayPresented ? "Close Benchmark" : "Open Benchmark").mtplxLocalized) {
                     if router.benchmarkOverlayPresented {
                         router.closeBenchmark()
                     } else {
@@ -355,7 +355,7 @@ struct MTPLXApp: App {
                     _ = chatViewModel.createNewConversation()
                 }
                 .keyboardShortcut("n", modifiers: [.command])
-                Button(router.chatSidebarCollapsed ? "Show Sidebar" : "Hide Sidebar") {
+                Button((router.chatSidebarCollapsed ? "Show Sidebar" : "Hide Sidebar").mtplxLocalized) {
                     withAnimation(.smooth(duration: 0.22)) {
                         router.chatSidebarCollapsed.toggle()
                     }

apps/MTPLXApp/Sources/MTPLXAppHost/Helpers/Localization.swift

@@ -0,0 +1,10 @@
+import Foundation
+
+extension String {
+    /// Looks up a runtime-provided UI label in the app's localization table.
+    /// SwiftUI localizes string literals automatically, but labels passed
+    /// through reusable components arrive as plain `String` values.
+    var mtplxLocalized: String {
+        Bundle.main.localizedString(forKey: self, value: self, table: nil)
+    }
+}

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Benchmark/BenchHeaderStat.swift

@@ -13,7 +13,7 @@ struct BenchHeaderStat: View {
 
     var body: some View {
         VStack(alignment: .leading, spacing: 2) {
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.system(size: 9, weight: .heavy, design: .monospaced))
                 .tracking(1.4)
                 .foregroundStyle(Brand.typeTertiary)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Benchmark/BenchPrimaryCTA.swift

@@ -48,7 +48,7 @@ struct BenchPrimaryCTA: View {
         HStack(spacing: 6) {
             Image(systemName: icon)
                 .font(.system(size: 11, weight: .heavy))
-            Text(title)
+            Text(title.mtplxLocalized)
                 .lineLimit(1)
                 .contentTransition(.opacity)
         }

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Benchmark/BenchSummaryCard.swift

@@ -114,7 +114,7 @@ struct BenchSummaryCard: View {
 
     private func metaRow(label: String, value: String) -> some View {
         HStack(spacing: 10) {
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.system(size: 9, weight: .heavy, design: .monospaced))
                 .tracking(1.4)
                 .foregroundStyle(Brand.typeTertiary)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Benchmark/BenchTelemetryCell.swift

@@ -38,7 +38,7 @@ struct BenchTelemetryCell: View {
 
     var body: some View {
         VStack(alignment: .leading, spacing: 2) {
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.system(size: 9, weight: .heavy, design: .monospaced))
                 .tracking(1.4)
                 .foregroundStyle(Brand.typeTertiary)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Chat/Primitives/SourcesFooterView.swift

@@ -51,7 +51,7 @@ struct SourcesFooterView: View {
             HStack(spacing: 6) {
                 Image(systemName: "link")
                     .font(.system(size: 10, weight: .medium))
-                Text("\(sources.count) source\(sources.count == 1 ? "" : "s")")
+                Text(sourceCountLabel)
                     .font(.system(size: 12, weight: .medium, design: .rounded))
                 Image(systemName: "chevron.right")
                     .font(.system(size: 9, weight: .semibold))
@@ -68,12 +68,25 @@ struct SourcesFooterView: View {
             .contentShape(Capsule())
         }
         .buttonStyle(.plain)
-        .help(isExpanded ? "Hide sources" : "Show all \(sources.count) sources")
+        .help(isExpanded ? "Hide sources".mtplxLocalized : showAllSourcesLabel)
         .accessibilityLabel(
-            isExpanded ? "Hide sources" : "Show \(sources.count) sources"
+            isExpanded ? "Hide sources".mtplxLocalized : showSourcesLabel
         )
     }
 
+    private var sourceCountLabel: String {
+        let key = sources.count == 1 ? "%d source" : "%d sources"
+        return String(format: key.mtplxLocalized, sources.count)
+    }
+
+    private var showAllSourcesLabel: String {
+        String(format: "Show all %d sources".mtplxLocalized, sources.count)
+    }
+
+    private var showSourcesLabel: String {
+        String(format: "Show %d sources".mtplxLocalized, sources.count)
+    }
+
     private func sourcePill(index: Int, source: SourceRecord) -> some View {
         Button {
             guard let url = URL(string: source.url) else { return }
@@ -102,6 +115,12 @@ struct SourcesFooterView: View {
         }
         .buttonStyle(.plain)
         .help(source.title.isEmpty ? source.url : source.title)
-        .accessibilityLabel("Open source \(index): \(source.domain)")
+        .accessibilityLabel(
+            String(
+                format: "Open source %1$d: %2$@".mtplxLocalized,
+                index,
+                source.domain
+            )
+        )
     }
 }

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Chrome.swift

@@ -14,13 +14,13 @@ struct DaemonStatePill: View {
         return HStack(spacing: 6) {
             stateDot
                 .frame(width: 8, height: 8)
-            Text(kind.label.uppercased())
+            Text(kind.label.mtplxLocalized.uppercased())
                 .font(.system(size: 10, weight: .heavy, design: .monospaced))
                 .tracking(1.5)
             if let detail {
                 Text("·")
                     .foregroundStyle(Brand.textHighlight.opacity(0.4))
-                Text(detail)
+                Text(detail.mtplxLocalized)
                     .font(.caption2)
                     .foregroundStyle(Brand.textHighlight.opacity(0.65))
                     .lineLimit(1)
@@ -37,7 +37,7 @@ struct DaemonStatePill: View {
                 )
         )
         .foregroundStyle(tint)
-        .help(helpText)
+        .help(helpText.mtplxLocalized)
     }
 
     private var tint: Color {
@@ -115,13 +115,13 @@ struct ConnectionDot: View {
                 }
             }
             .frame(width: 14, height: 14)
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.system(size: 11, weight: .semibold, design: .monospaced))
                 .tracking(0.5)
                 .foregroundStyle(tint.opacity(0.95))
         }
         .onChange(of: stateKey) { _, _ in pulseKey &+= 1 }
-        .help(helpText)
+        .help(helpText.mtplxLocalized)
     }
 
     /// True only when both the daemon is `.running` and the SSE stream

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/AcceptanceReveal.swift

@@ -255,7 +255,7 @@ private struct ARBaselineRow: View {
 
     var body: some View {
         HStack(spacing: 10) {
-            Text(row.label)
+            Text(row.label.mtplxLocalized)
                 .font(.system(size: 10, weight: .heavy, design: .monospaced))
                 .foregroundStyle(Brand.typeTertiary)
                 .frame(width: 24, alignment: .leading)
@@ -276,7 +276,7 @@ private struct AcceptanceBarRow: View {
 
     var body: some View {
         HStack(spacing: 10) {
-            Text(row.label)
+            Text(row.label.mtplxLocalized)
                 .font(.system(size: 10, weight: .heavy, design: .monospaced))
                 .foregroundStyle(row.isWinner ? Brand.typeHi : Brand.typeSecondary)
                 .frame(width: 24, alignment: .leading)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/Card.swift

@@ -50,12 +50,12 @@ struct Card<Content: View>: View {
                 HStack(alignment: .firstTextBaseline) {
                     VStack(alignment: .leading, spacing: 2) {
                         if let title {
-                            Text(title)
+                            Text(title.mtplxLocalized)
                                 .font(.headline)
                                 .foregroundStyle(.primary)
                         }
                         if let subtitle {
-                            Text(subtitle)
+                            Text(subtitle.mtplxLocalized)
                                 .font(.caption)
                                 .foregroundStyle(.secondary)
                         }

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/EmptyStateView.swift

@@ -19,16 +19,16 @@ struct EmptyStateView: View {
             Image(systemName: symbol)
                 .font(.system(size: 36, weight: .light))
                 .foregroundStyle(Brand.typeBody.opacity(0.45))
-            Text(title)
+            Text(title.mtplxLocalized)
                 .font(.system(.title3, design: .rounded).weight(.bold))
                 .chromeText()
-            Text(message)
+            Text(message.mtplxLocalized)
                 .font(.callout)
                 .foregroundStyle(Brand.typeBody.opacity(0.7))
                 .multilineTextAlignment(.center)
                 .frame(maxWidth: 360, minHeight: 38)
             if let action {
-                Button(actionLabel, action: action)
+                Button(actionLabel.mtplxLocalized, action: action)
                     .controlSize(.large)
                     .buttonStyle(.borderedProminent)
                     .tint(Brand.accentChrome)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/FormRow.swift

@@ -28,11 +28,11 @@ struct FormRow<Content: View>: View {
     var body: some View {
         HStack(alignment: .firstTextBaseline, spacing: 12) {
             VStack(alignment: .leading, spacing: 3) {
-                Text(label)
+                Text(label.mtplxLocalized)
                     .font(.system(.callout))
                     .foregroundStyle(Brand.typeBody)
                 if let caption {
-                    Text(caption)
+                    Text(caption.mtplxLocalized)
                         .font(.caption2)
                         .foregroundStyle(Brand.typeTertiary)
                         .fixedSize(horizontal: false, vertical: true)
@@ -57,11 +57,11 @@ struct FormToggleRow: View {
     var body: some View {
         HStack(alignment: .firstTextBaseline, spacing: 12) {
             VStack(alignment: .leading, spacing: 3) {
-                Text(label)
+                Text(label.mtplxLocalized)
                     .font(.system(.callout))
                     .foregroundStyle(Brand.typeBody)
                 if let caption {
-                    Text(caption)
+                    Text(caption.mtplxLocalized)
                         .font(.caption2)
                         .foregroundStyle(Brand.typeTertiary)
                         .fixedSize(horizontal: false, vertical: true)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/HBarRow.swift

@@ -23,7 +23,7 @@ struct HBarRow: View {
     var body: some View {
         VStack(alignment: .leading, spacing: 4) {
             HStack {
-                Text(label)
+                Text(label.mtplxLocalized)
                     .font(.system(.caption, design: .rounded).weight(.bold))
                     .foregroundStyle(Brand.typeBody)
                 Spacer()

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/MetricRow.swift

@@ -14,7 +14,7 @@ struct MetricRow: View {
 
     var body: some View {
         HStack {
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.callout)
                 .foregroundStyle(Brand.typeBody.opacity(0.75))
             Spacer(minLength: 8)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/MicroHeader.swift

@@ -21,7 +21,7 @@ struct MicroHeader: View {
                     .font(.system(size: 10, weight: .medium))
                     .foregroundStyle(Brand.typeTertiary)
             }
-            Text(text.uppercased())
+            Text(text.uppercased().mtplxLocalized)
                 .font(.system(size: 10, weight: .heavy, design: .monospaced))
                 .tracking(1.5)
                 .foregroundStyle(Brand.typeTertiary)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/PillBadge.swift

@@ -19,7 +19,7 @@ struct PillBadge: View {
                 Image(systemName: systemImage)
                     .font(.caption2)
             }
-            Text(text)
+            Text(text.mtplxLocalized)
                 .font(.caption.weight(.medium))
         }
         .foregroundStyle(emphasized ? tint : .primary)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Common/StatTile.swift

@@ -24,7 +24,7 @@ struct StatTile: View {
                         .font(.system(size: 10, weight: .medium))
                         .foregroundStyle(Brand.typeTertiary)
                 }
-                Text(label.uppercased())
+                Text(label.uppercased().mtplxLocalized)
                     .font(.system(size: 10, weight: .heavy, design: .monospaced))
                     .tracking(1.5)
                     .foregroundStyle(Brand.typeTertiary)
@@ -48,7 +48,7 @@ struct StatTile: View {
                 }
             }
             if let caption {
-                Text(caption)
+                Text(caption.mtplxLocalized)
                     .font(.system(size: 10, weight: .medium, design: .monospaced))
                     .foregroundStyle(Brand.typeTertiary)
                     .lineLimit(1)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Components/FanModeToggle.swift

@@ -56,7 +56,7 @@ struct FanModeToggle: View {
         Button {
             apply(value)
         } label: {
-            Text(label)
+            Text(label.mtplxLocalized)
                 .font(.system(size: 10, weight: .heavy, design: .monospaced))
                 .tracking(1)
                 .foregroundStyle(active == value ? Brand.bgOuter : Brand.textHighlight)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Forge/ForgeCreateView.swift

@@ -234,11 +234,11 @@ struct ForgeStageShell<Content: View, Footer: View>: View {
 
     private var header: some View {
         VStack(alignment: .leading, spacing: 6) {
-            Text(title)
+            Text(title.mtplxLocalized)
                 .font(.system(.title2, design: .rounded).weight(.semibold))
                 .foregroundStyle(Brand.typeHi)
             if let subtitle, !subtitle.isEmpty {
-                Text(subtitle)
+                Text(subtitle.mtplxLocalized)
                     .font(.system(size: 13))
                     .foregroundStyle(Brand.typeSecondary)
                     .fixedSize(horizontal: false, vertical: true)
@@ -275,6 +275,11 @@ struct ForgeStageShell<Content: View, Footer: View>: View {
     private var progressCapsule: some View {
         let allCases = ForgeStep.allCases
         let stepIndex = allCases.firstIndex(of: step) ?? 0
+        let stepProgress = String(
+            format: "Step %d of %d".mtplxLocalized,
+            stepIndex + 1,
+            allCases.count
+        )
         return VStack(spacing: 8) {
             ZStack(alignment: .leading) {
                 Capsule()
@@ -286,12 +291,12 @@ struct ForgeStageShell<Content: View, Footer: View>: View {
                     .animation(.spring(response: 0.45, dampingFraction: 0.85), value: stepIndex)
             }
             .accessibilityHidden(true)
-            Text("\(progressLabel(for: step))  ·  Step \(stepIndex + 1) of \(allCases.count)")
+            Text("\(progressLabel(for: step).mtplxLocalized)  ·  \(stepProgress)")
                 .font(.system(size: 11, weight: .medium, design: .monospaced))
                 .tracking(0.6)
                 .foregroundStyle(Brand.typeTertiary)
                 .contentTransition(.numericText())
-                .accessibilityLabel("Step \(stepIndex + 1) of \(allCases.count)")
+                .accessibilityLabel(stepProgress)
         }
     }
 
@@ -335,7 +340,7 @@ struct ForgePrimaryButton: View {
     var body: some View {
         Button(action: action) {
             HStack(spacing: 7) {
-                Text(title)
+                Text(title.mtplxLocalized)
                     .font(.system(size: 13.5, weight: .semibold))
                     .contentTransition(.opacity)
                 if let icon {
@@ -382,7 +387,7 @@ struct ForgePrimaryButton: View {
         }
         .buttonStyle(.plain)
         .disabled(!isEnabled)
-        .accessibilityLabel(title)
+        .accessibilityLabel(title.mtplxLocalized)
         .onHover { hovering in isHovering = hovering && isEnabled }
         .gesture(
             DragGesture(minimumDistance: 0)

apps/MTPLXApp/Sources/MTPLXAppHost/Views/Forge/ForgeTabHeader.swift

@@ -79,7 +79,7 @@ struct ForgeTabHeader: View {
             HStack(spacing: 5) {
                 Image(systemName: icon)
                     .font(.system(size: 10.5, weight: .semibold))
-                Text(label)
+                Text(label.mtplxLocalized)
                     .font(.system(size: 11.5, weight: .semibold))
             }
             .foregroundStyle(isActive ? Brand.typeHi : Brand.typeSecondary)
@@ -119,7 +119,7 @@ struct ForgeTabHeader: View {
             HStack(spacing: 5) {
                 Image(systemName: isMidBuild ? "arrow.forward" : "plus")
                     .font(.system(size: 10.5, weight: .heavy))
-                Text(isMidBuild ? "Continue build" : "New build")
+                Text((isMidBuild ? "Continue build" : "New build").mtplxLocalized)
                     .font(.system(size: 11.5, weight: .semibold))
                     .lineLimit(1)
             }
@@ -133,8 +133,8 @@ struct ForgeTabHeader: View {
             .contentShape(Capsule())
         }
         .buttonStyle(.plain)
-        .help(isMidBuild
+        .help((isMidBuild
               ? "A build is in progress — jump back to it"
-              : "Start a new build")
+              : "Start a new build").mtplxLocalized)
     }
 }