feat(companion): add runtime event subscription hooks

src/companion/runtimeClient.test.ts

@@ -96,6 +96,61 @@ afterAll(async () => {
 });
 
 describe('CompanionRuntimeClient', () => {
+  it('dispatches gateway events to subscribed handlers and supports unsubscribe', () => {
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+    const handler = vi.fn();
+    const unsubscribe = client.subscribeEvents(handler);
+
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 42,
+        event: 'agent.stream',
+        data: { token: 'hello' },
+      }),
+    );
+
+    expect(handler).toHaveBeenCalledWith('agent.stream', { token: 'hello' });
+
+    unsubscribe();
+
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 43,
+        event: 'agent.stream',
+        data: { token: 'world' },
+      }),
+    );
+
+    expect(handler).toHaveBeenCalledTimes(1);
+  });
+
+  it('isolates subscriber callback failures', () => {
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+    const badHandler = vi.fn(() => {
+      throw new Error('subscriber failed');
+    });
+    const goodHandler = vi.fn();
+    client.subscribeEvents(badHandler);
+    client.subscribeEvents(goodHandler);
+
+    expect(() => {
+      (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+        JSON.stringify({
+          id: 44,
+          event: 'agent.stream',
+          data: { token: 'safe' },
+        }),
+      );
+    }).not.toThrow();
+
+    expect(badHandler).toHaveBeenCalledOnce();
+    expect(goodHandler).toHaveBeenCalledWith('agent.stream', { token: 'safe' });
+  });
+
   it('connects and performs node registration + capability discovery', async () => {
     if (!LISTEN_ALLOWED) {
       return;