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

src/cli/send.ts

@@ -0,0 +1,12 @@
+import type { Command } from 'commander';
+
+export function registerSendCommand(program: Command): void {
+  program
+    .command('send <message>')
+    .description('Send a one-shot message and print the response')
+    .option('-c, --config <path>', 'Config file path')
+    .action(async (_message: string, _opts: { config?: string }) => {
+      console.error('Not yet implemented');
+      process.exit(1);
+    });
+}