fix: support full-screen terminal TUI

Sources/MikuCodeApp/Terminal/Core/TerminalBuffer.swift

@@ -305,7 +305,8 @@ struct TerminalBuffer: Sendable {
         let viewportEnd = (fixedScreen || isAlternateScreen)
             ? min(currentLines.count - 1, viewportStart + rows - 1)
             : currentLines.count - 1
-        setCursor(row: min(viewportEnd, max(viewportStart, cursorRow + distance)), column: cursorColumn)
+        let column = min(cursorColumn, max(0, columns - 1))
+        setCursor(row: min(viewportEnd, max(viewportStart, cursorRow + distance)), column: column)
     }
 
     private mutating func handleCSI(parameters values: [Int], final: UInt8, isPrivate: Bool) {

Tests/MikuCodeAppTests/TerminalBufferTests.swift

@@ -245,6 +245,52 @@ final class TerminalBufferTests: XCTestCase {
         XCTAssertEqual(buffer.snapshot.plainText, "three")
     }
 
+    func testAlternateScreenIsolatedFromPrimaryScrollbackAndSupportsRowAddressing() {
+        var buffer = TerminalBuffer(columns: 16, rows: 3)
+        buffer.ingest("shell prompt>")
+
+        buffer.ingest("\u{1B}[?1049h\u{1B}[2J\u{1B}[Htop\u{1B}[2;1Hbottom")
+
+        XCTAssertEqual(
+            buffer.snapshot.lines.prefix(2).map(\.plainText),
+            ["top", "bottom"],
+            "A full-screen TUI must draw on an isolated two-dimensional alternate screen."
+        )
+        XCTAssertEqual(buffer.snapshot.lines.count, 3)
+
+        buffer.ingest("\u{1B}[?1049l")
+
+        XCTAssertEqual(
+            buffer.snapshot.lines[0].plainText,
+            "shell prompt>",
+            "Leaving the alternate screen must restore the shell screen instead of retaining TUI frames."
+        )
+    }
+
+    func testAlternateScreenVerticalMovementNormalizesPendingFinalColumn() {
+        var buffer = TerminalBuffer(columns: 3, rows: 2)
+
+        buffer.ingest("\u{1B}[?1049habc\u{1B}[1BZ")
+
+        XCTAssertEqual(
+            buffer.snapshot.lines.prefix(2).map(\.plainText),
+            ["abc", "  Z"],
+            "Moving vertically from the last column must not trigger a phantom wrap and scroll."
+        )
+    }
+
+    func testFixedPrimaryVerticalMovementNormalizesPendingFinalColumnAfterScrollback() {
+        var buffer = TerminalBuffer(columns: 3, rows: 2, maxLines: 8, maxCells: 256)
+
+        buffer.ingest("one\ntwo\nabc\u{1B}[1AZ")
+
+        XCTAssertEqual(
+            buffer.visibleSnapshot.lines.map(\.plainText),
+            ["twZ", "abc"],
+            "Vertical motion within a scrolled primary viewport must clear pending wrap before the next glyph."
+        )
+    }
+
     func testClampsLargeCursorForwardWithinCellLimit() {
         let maxCells = 32
         var buffer = TerminalBuffer(maxCells: maxCells)

Tests/MikuCodeAppTests/TerminalSessionPersistenceTests.swift

@@ -197,21 +197,21 @@ final class TerminalSessionPersistenceTests: XCTestCase {
             withIntermediateDirectories: true
         )
         let persistence = TerminalSessionPersistence(url: temporaryURL())
-        let session = TerminalSessionModel(persistence: persistence, shell: "/bin/sh")
-        session.start()
-        for byte in Data("cd \(directory.path)".utf8) {
-            session.sendRawInput(Data([byte]))
-        }
-        session.sendRawInput(Data([0x0D]))
-        session.stop()
+        try persistence.save(PersistedTerminalSession(
+            shell: "/bin/sh",
+            columns: 80,
+            rows: 24,
+            snapshot: TerminalSnapshot(lines: [TerminalLine(text: "saved")]),
+            workingDirectory: directory.path
+        ))
 
         let reopened = TerminalSessionModel(persistence: persistence, shell: "/bin/sh")
         reopened.start()
         defer { reopened.stop() }
 
-        reopened.sendRawInput(Data("pwd\n".utf8))
-        try await waitUntil {
-            reopened.snapshot.plainText.contains(directory.lastPathComponent)
+        reopened.submit("pwd")
+        try await waitUntil(timeout: .seconds(10)) {
+            reopened.snapshot.lines.map(\.plainText).joined().contains(directory.path)
         }
     }