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/tui/test/virtual-terminal.ts

@@ -86,6 +86,11 @@ export class VirtualTerminal implements Terminal {
 		this.xterm.write("\x1b[2J\x1b[H"); // Clear screen and move to home (1,1)
 	}
 
+	setTitle(title: string): void {
+		// OSC 0;title BEL - set terminal window title
+		this.xterm.write(`\x1b]0;${title}\x07`);
+	}
+
 	// Test-specific methods not in Terminal interface
 
 	/**