fix(tui): restored compact editor border by default

- Restored the compact two-row `Editor` layout by default and gated the dedicated IME-safe bottom border behind `setImeSafeCursorLayout()`.
- Added `tui.imeSafeCursor` as an opt-in appearance setting and applied it to initial and replacement editors.
- Added regression coverage for compact default rendering while retaining terminal-local IME preedit protection.
- Updated the TUI changelog for the opt-in compatibility layout.

packages/coding-agent/src/config/settings-schema.ts

@@ -982,6 +982,17 @@ export const SETTINGS_SCHEMA = {
 		},
 	},
 
+	"tui.imeSafeCursor": {
+		type: "boolean",
+		default: false,
+		ui: {
+			tab: "appearance",
+			group: "Display",
+			label: "IME-Safe Prompt Layout",
+			description: "Move the prompt's bottom border to a separate row so macOS IME preedit cannot displace it",
+		},
+	},
+
 	// ────────────────────────────────────────────────────────────────────────
 	// Model
 	// ────────────────────────────────────────────────────────────────────────

packages/coding-agent/src/modes/interactive-mode.ts

@@ -680,6 +680,7 @@ export class InteractiveMode implements InteractiveModeContext {
 		this.errorBannerContainer = new AnchoredLiveContainer();
 		this.modelCycleContainer = new AnchoredLiveContainer();
 		this.editor = new CustomEditor(getEditorTheme());
+		this.editor.setImeSafeCursorLayout(settings.get("tui.imeSafeCursor"));
 		this.editor.setUseTerminalCursor(this.ui.getShowHardwareCursor());
 		this.editor.setAutocompleteMaxVisible(settings.get("autocompleteMaxVisible"));
 		this.editor.onAutocompleteCancel = () => {
@@ -3669,6 +3670,7 @@ export class InteractiveMode implements InteractiveModeContext {
 		factory: ((tui: TUI, theme: EditorTheme, keybindings: KeybindingsManager) => CustomEditor) | undefined,
 	): void {
 		const previousEditor = this.editor;
+		nextEditor.setImeSafeCursorLayout(this.settings.get("tui.imeSafeCursor"));
 		const previousText = previousEditor.getText();
 		const nextEditor = factory
 			? factory(this.ui, getEditorTheme(), this.keybindings)