feat(vela): add mocked turn transcript response slice

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

@@ -326,3 +326,82 @@ test('websocket handles valid and invalid client messages safely', async () => {
 		await server.close();
 	}
 });
+
+test('websocket mocked turn emits deterministic transcript and response events in order', async () => {
+	const server = await startServer();
+
+	try {
+		const client = await connectWebSocket(server.port);
+		await client.nextMessage();
+		await client.nextMessage();
+
+		client.sendJson({ type: 'mocked.turn.trigger', payload: {} });
+
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'listening' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'transcript.final',
+			payload: { text: '[mocked user] What is the current mocked vertical slice?' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'thinking' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'speaking' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'response.text.delta',
+			payload: { text: '[mocked assistant] ' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'response.text.delta',
+			payload: { text: 'This is a deterministic mocked response from the gateway vertical slice.' }
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'response.completed',
+			payload: {}
+		});
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'idle' }
+		});
+
+		await client.close();
+	} finally {
+		await server.close();
+	}
+});
+
+test('websocket rejects a second mocked turn while one is in flight', async () => {
+	const server = await startServer();
+
+	try {
+		const client = await connectWebSocket(server.port);
+		await client.nextMessage();
+		await client.nextMessage();
+
+		client.sendJson({ type: 'mocked.turn.trigger', payload: {} });
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'session.state',
+			payload: { value: 'listening' }
+		});
+
+		client.sendJson({ type: 'mocked.turn.trigger', payload: {} });
+		assert.deepEqual(await client.nextMessage(), {
+			type: 'error',
+			payload: {
+				code: 'mocked_turn_in_flight',
+				message: 'Only one mocked turn can run per session at a time.',
+				retryable: true
+			}
+		});
+
+		await client.close();
+	} finally {
+		await server.close();
+	}
+});