feat(vela-ui): add placeholder push-to-talk control shell

apps/vela-gateway/test/websocket-session.test.js

@@ -327,6 +327,38 @@ test('websocket handles valid and invalid client messages safely', async () => {
 	}
 });
 
+test('websocket accepts a placeholder input cycle before a mocked turn on the same socket', async () => {
+	const server = await startServer();
+
+	try {
+		const client = await connectWebSocket(server.port);
+		await client.nextMessage();
+		await client.nextMessage();
+
+		client.sendJson({ type: 'input_audio.append', payload: { chunk: 'placeholder-control-shell-chunk' } });
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'listening' }
+		});
+
+		client.sendJson({ type: 'input_audio.commit', payload: {} });
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'idle' }
+		});
+
+		client.sendJson({ type: 'mocked.turn.trigger', payload: {} });
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'listening' }
+		});
+
+		await client.close();
+	} finally {
+		await server.close();
+	}
+});
+
 test('websocket mocked turn emits deterministic transcript and response events in order', async () => {
 	const server = await startServer();