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/src/terminal.ts

@@ -26,6 +26,9 @@ export interface Terminal {
 	clearLine(): void; // Clear current line
 	clearFromCursor(): void; // Clear from cursor to end of screen
 	clearScreen(): void; // Clear entire screen and move cursor to (0,0)
+
+	// Title operations
+	setTitle(title: string): void; // Set terminal window title
 }
 
 /**
@@ -127,4 +130,9 @@ export class ProcessTerminal implements Terminal {
 	clearScreen(): void {
 		process.stdout.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
+		process.stdout.write(`\x1b]0;${title}\x07`);
+	}
 }