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
 	// ────────────────────────────────────────────────────────────────────────