feat(tui): add terminal user interface with Ink

Add a full TUI for Claudeman using Ink (React for CLI):
- StartScreen: Shows existing sessions from screens.json
- TabBar: Session tabs with status indicators
- TerminalView: PTY output display with scrolling
- StatusBar: Session info and keyboard shortcuts
- HelpOverlay: Full keyboard shortcut reference

Features:
- Session discovery from ~/.claudeman/screens.json
- Tab navigation (Ctrl+Tab, Ctrl+1-9)
- Create new sessions (connects to web API)
- Kill sessions via screen commands
- Keyboard-driven navigation

Usage: claudeman tui

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cli.ts

@@ -470,4 +470,18 @@ program
     }
   });
 
+// TUI command
+program
+  .command('tui')
+  .description('Start the terminal user interface')
+  .action(async () => {
+    try {
+      const { startTUI } = await import('./tui/index.js');
+      await startTUI();
+    } catch (err) {
+      console.error(chalk.red(`✗ Failed to start TUI: ${(err as Error).message}`));
+      process.exit(1);
+    }
+  });
+
 export { program };