feat(companion): add publishHeartbeat helper across platform clients

src/companion/platformClients.test.ts

@@ -168,4 +168,19 @@ describe('platform companion clients', () => {
       capabilities: expect.any(Object),
     });
   });
+
+  it('publishHeartbeat uses safe defaults for status payload', async () => {
+    const mock = createRuntimeMock();
+    const client = new AndroidCompanionClient({ runtime: mock.runtime, nodeId: 'android-node' });
+
+    await client.publishHeartbeat();
+
+    expect(mock.setNodeStatus).toHaveBeenCalledWith(
+      expect.objectContaining({
+        platform: 'android',
+        statusText: 'heartbeat',
+        powerSource: 'unknown',
+      }),
+    );
+  });
 });