feat: refine coding agent workspace

DESIGN.md

@@ -33,8 +33,8 @@ use the close transition and return to `idle`.
   reveals a small speech-bubble terminal affordance. The companion never walks,
   slides, or bobs in idle; only the intentional gaze state changes.
   Clicking either Miku herself or that bubble begins the terminal transition.
-- In terminal state, the bubble opens as a coding-agent workspace: the centered
-  MikuCode mark gives way to prompt history, a provider/approval composer, and
+- In terminal state, the bubble opens as a coding-agent workspace: a compact
+  MikuCode logo mark gives way to prompt history, a provider/approval composer, and
   a terminal toggle. Codex and Claude support `Plan`, `Accept`, and `Auto`;
   the workspace only records a request after its token-matched PTY delivery.
   The terminal toggle reveals that same local PTY inside the bubble—never a
@@ -44,11 +44,17 @@ use the close transition and return to `idle`.
   companion at the floating layer; it only returns behind other apps after the
   app itself loses focus, and never quits MikuCode.
 - The workspace header is an agent-workspace cue, not a toolbar: it contains
-  the app name, an embedded-terminal toggle, and one close control. The
-  composer is the only persistent input surface. Command-F opens the only
+  the logo mark, local-shell status, an embedded-terminal toggle, and one close
+  control. The composer is a measured bottom dock: provider and approval chips
+  remain distinct from a full-width prompt field and labelled send action at all
+  supported bubble sizes. Codex uses a cool gray signal, Claude orange, and
+  Plan/Accept/Auto each retain distinct semantic colors. Command-F opens the only
   transient terminal text field: a compact in-bubble finder. Command-G and
   Shift-Command-G navigate its case-insensitive matches across output pages;
   Escape restores terminal focus and removes the finder.
+- The speech-bubble tail owns a reserved header inset; terminal and close controls
+  never sit beneath it, and the focused-Miku close target begins after a fixed gap
+  beyond the workspace frame. No interactive target is allowed to overlap another.
 - The speech bubble resizes directly from its edges and corners. Its frame stays
   inside a 24-point display inset and preserves a minimum right-side Miku rail;
   native directional cursors expose the otherwise unobtrusive resize targets.
@@ -71,10 +77,10 @@ snapshot persist on close and restore on the next launch.
 ## Visual tokens
 
 The visual system uses a 4-point spacing base. Idle is transparent; active
-surfaces use flat dark sky-blue tones, a translucent cyan rim, a restrained
-teal shadow, and white terminal text. The header uses compact rounded app type
-with small monospaced agent labels, making the surface read as a coding-agent
-workspace rather than a generic terminal emulator. The app icon is a separate
+surfaces use flat dark sky-blue tones, a translucent cyan rim with a slow opacity
+pulse, a restrained teal shadow, and white terminal text. The header uses modern
+SF app type with small monospaced agent labels, making the surface read as a
+coding-agent workspace rather than a generic terminal emulator. The app icon is a separate
 terminal-and-Miku asset; the desktop companion contains only the 2D Miku
 character. Idle artwork stays centered and still above a subtle teal ground
 shadow. Its only idle motion is an intentional crossfade to an attentive gaze

Sources/MikuCodeApp/Agent/AgentWorkspaceModel.swift

@@ -18,6 +18,24 @@ enum AgentProvider: String, CaseIterable, Identifiable {
         }
     }
 
+    var tint: Color {
+        switch self {
+        case .codex: Color(red: 0.720, green: 0.780, blue: 0.860)
+        case .claude: Color(red: 1.000, green: 0.590, blue: 0.300)
+        case .pi: Color(red: 0.740, green: 0.520, blue: 1.000)
+        case .openCode: Color(red: 0.400, green: 0.880, blue: 0.650)
+        }
+    }
+
+    var symbol: String {
+        switch self {
+        case .codex: "circle.hexagongrid.fill"
+        case .claude: "sun.max.fill"
+        case .pi: "circle.grid.cross.fill"
+        case .openCode: "chevron.left.forwardslash.chevron.right"
+        }
+    }
+
     var supportsApproval: Bool {
         self == .codex || self == .claude
     }
@@ -37,6 +55,22 @@ enum AgentApproval: String, CaseIterable, Identifiable {
         case .auto: "Auto"
         }
     }
+
+    var tint: Color {
+        switch self {
+        case .plan: Color(red: 0.640, green: 0.610, blue: 1.000)
+        case .accept: Color(red: 0.310, green: 0.820, blue: 1.000)
+        case .auto: Color(red: 1.000, green: 0.690, blue: 0.300)
+        }
+    }
+
+    var symbol: String {
+        switch self {
+        case .plan: "map.fill"
+        case .accept: "checkmark.shield.fill"
+        case .auto: "bolt.fill"
+        }
+    }
 }
 
 struct AgentRunRequest: Equatable {