feat(companion): add filtered runtime event subscription helper

src/companion/runtimeClient.test.ts

@@ -151,6 +151,42 @@ describe('CompanionRuntimeClient', () => {
     expect(goodHandler).toHaveBeenCalledWith('agent.stream', { token: 'safe' });
   });
 
+  it('supports filtered subscribeEvent helper', () => {
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+    const streamHandler = vi.fn();
+    const unsubscribe = client.subscribeEvent<{ token: string }>('agent.stream', streamHandler);
+
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 45,
+        event: 'agent.stream',
+        data: { token: 'first' },
+      }),
+    );
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 46,
+        event: 'agent.typing',
+        data: { active: true },
+      }),
+    );
+
+    expect(streamHandler).toHaveBeenCalledTimes(1);
+    expect(streamHandler).toHaveBeenCalledWith({ token: 'first' });
+
+    unsubscribe();
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 47,
+        event: 'agent.stream',
+        data: { token: 'second' },
+      }),
+    );
+    expect(streamHandler).toHaveBeenCalledTimes(1);
+  });
+
   it('connects and performs node registration + capability discovery', async () => {
     if (!LISTEN_ALLOWED) {
       return;