Add terminal title support to TUI framework (#407)

Add setTitle() method to Terminal interface for setting window title.
Uses standard OSC escape sequence \x1b]0;...\x07 for broad terminal
compatibility (macOS Terminal, iTerm2, Kitty, WezTerm, Ghostty, etc.).

Changes:
- Add setTitle(title: string) to Terminal interface
- Implement in ProcessTerminal using OSC sequence
- Implement no-op in VirtualTerminal for testing
- Use in interactive mode to set title as "pi - <dirname>"

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

@@ -303,6 +303,10 @@ export class InteractiveMode {
 		this.ui.start();
 		this.isInitialized = true;
 
+		// Set terminal title
+		const cwdBasename = path.basename(process.cwd());
+		this.ui.terminal.setTitle(`pi - ${cwdBasename}`);
+
 		// Initialize hooks with TUI-based UI context
 		await this.initHooksAndCustomTools();