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/tui/index.tsx

@@ -0,0 +1,41 @@
+/**
+ * @fileoverview TUI entry point for Claudeman
+ *
+ * Renders the terminal user interface using Ink (React for CLI).
+ * This provides a full-screen TUI similar to the web interface,
+ * with tabs for sessions and real-time terminal output.
+ */
+
+import React from 'react';
+import { render } from 'ink';
+import { App } from './App.js';
+
+/**
+ * Checks if the terminal supports raw mode (required for TUI)
+ */
+function isRawModeSupported(): boolean {
+  return Boolean(
+    process.stdin.isTTY &&
+    typeof process.stdin.setRawMode === 'function'
+  );
+}
+
+/**
+ * Starts the TUI application
+ * @returns Promise that resolves when the app exits
+ */
+export async function startTUI(): Promise<void> {
+  // Check if we're in an interactive terminal
+  if (!isRawModeSupported()) {
+    console.error('Error: TUI requires an interactive terminal with TTY support.');
+    console.error('Make sure you are running this command in a real terminal, not piped.');
+    process.exit(1);
+  }
+
+  // Clear the terminal for full-screen experience
+  process.stdout.write('\x1b[2J\x1b[H');
+
+  const { waitUntilExit } = render(<App />);
+
+  await waitUntilExit();
+}