feat(cli): add CLI entry point with commander and start command

src/cli/tui.ts

@@ -0,0 +1,13 @@
+import type { Command } from 'commander';
+
+export function registerTuiCommand(program: Command): void {
+  program
+    .command('tui')
+    .description('Launch the interactive TUI')
+    .option('-f, --fullscreen', 'Start in fullscreen mode')
+    .option('-c, --config <path>', 'Config file path')
+    .action(async (_opts: { fullscreen?: boolean; config?: string }) => {
+      console.error('Not yet implemented');
+      process.exit(1);
+    });
+}