worker.ts: ASSIGNMENT_TIMEOUT handler never resolves/rejects pending job promise — worker hangs forever + memory leak

[tsushanth]

Bug

In agents/src/worker.ts (around lines 853–862), the ASSIGNMENT_TIMEOUT message handler logs a warning and returns, but never resolves or rejects the PendingAssignment promise that is being awaited on line 859:

```ts
// ASSIGNMENT_TIMEOUT handler (simplified):
case AgentServerMessage_Message.Case.AssignmentTimeout:
logger.warn('assignment timeout');
return; // ← promise never settled

// ...
await this.#pending[req.id]?.promise; // ← hangs forever
```

Two problems result:

1. Permanent hang: await this.#pending[req.id]?.promise never resolves or rejects after a timeout fires. The worker goroutine for that job is permanently blocked.

2. Memory leak: The #pending[req.id] entry is only deleted on successful assignment (around line 698). On timeout, it is never cleaned up — each timed-out job leaks one entry from the #pending map for the lifetime of the worker.

Fix

Add a reject (or resolve) slot to the PendingAssignment type and call it in the timeout handler, then delete the entry:

```ts
case AgentServerMessage_Message.Case.AssignmentTimeout: {
const pending = this.#pending[req.id];
if (pending) {
delete this.#pending[req.id];
pending.reject(new Error(assignment timeout for job ${req.id}));
}
return;
}
```

Alternatively, use Promise.race with a timeout-rejection at the await site.

Impact

• Any job that times out during assignment permanently blocks a worker slot
• #pending map grows unbounded under sustained timeout conditions
• Worker process may eventually exhaust memory or become unresponsive