feat(tui): query Kitty keyboard protocol support before enabling

- Query terminal with CSI ? u before enabling Kitty protocol
- Only enable protocol if terminal responds (100ms timeout)
- Mode-aware key parsing: when Kitty active, interpret legacy
  sequences as custom terminal mappings (e.g. \x1b\r = shift+enter)
- Add Terminal Setup section to README with Ghostty/wezterm config

fixes #439

packages/tui/test/virtual-terminal.ts

@@ -55,6 +55,11 @@ export class VirtualTerminal implements Terminal {
 		return this._rows;
 	}
 
+	get kittyProtocolActive(): boolean {
+		// Virtual terminal always reports Kitty protocol as active for testing
+		return true;
+	}
+
 	moveBy(lines: number): void {
 		if (lines > 0) {
 			// Move down