fix: harden typing lifecycle and cross-channel suppression

src/channels/typing.test.ts

@@ -73,6 +73,80 @@ describe("createTypingCallbacks", () => {
     }
   });
 
+  it("stops keepalive after consecutive start failures", async () => {
+    vi.useFakeTimers();
+    try {
+      const start = vi.fn().mockRejectedValue(new Error("gone"));
+      const onStartError = vi.fn();
+      const callbacks = createTypingCallbacks({ start, onStartError });
+
+      await callbacks.onReplyStart();
+      expect(start).toHaveBeenCalledTimes(1);
+      expect(onStartError).toHaveBeenCalledTimes(1);
+
+      await vi.advanceTimersByTimeAsync(3_000);
+      expect(start).toHaveBeenCalledTimes(2);
+      expect(onStartError).toHaveBeenCalledTimes(2);
+
+      await vi.advanceTimersByTimeAsync(9_000);
+      expect(start).toHaveBeenCalledTimes(2);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  it("does not restart keepalive when breaker trips on initial start", async () => {
+    vi.useFakeTimers();
+    try {
+      const start = vi.fn().mockRejectedValue(new Error("gone"));
+      const onStartError = vi.fn();
+      const callbacks = createTypingCallbacks({
+        start,
+        onStartError,
+        maxConsecutiveFailures: 1,
+      });
+
+      await callbacks.onReplyStart();
+      expect(start).toHaveBeenCalledTimes(1);
+
+      await vi.advanceTimersByTimeAsync(9_000);
+      expect(start).toHaveBeenCalledTimes(1);
+      expect(onStartError).toHaveBeenCalledTimes(1);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  it("resets failure counter after a successful keepalive tick", async () => {
+    vi.useFakeTimers();
+    try {
+      let callCount = 0;
+      const start = vi.fn().mockImplementation(async () => {
+        callCount += 1;
+        if (callCount % 2 === 1) {
+          throw new Error("flaky");
+        }
+      });
+      const onStartError = vi.fn();
+      const callbacks = createTypingCallbacks({
+        start,
+        onStartError,
+        maxConsecutiveFailures: 2,
+      });
+
+      await callbacks.onReplyStart(); // fail
+      await vi.advanceTimersByTimeAsync(3_000); // success
+      await vi.advanceTimersByTimeAsync(3_000); // fail
+      await vi.advanceTimersByTimeAsync(3_000); // success
+      await vi.advanceTimersByTimeAsync(3_000); // fail
+
+      expect(start).toHaveBeenCalledTimes(5);
+      expect(onStartError).toHaveBeenCalledTimes(3);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it("deduplicates stop across idle and cleanup", async () => {
     const start = vi.fn().mockResolvedValue(undefined);
     const stop = vi.fn().mockResolvedValue(undefined);