fix(channel): cancel queued work under the agent-scoped session key - #3316

Fixes #3315

ChatChannel.produce() files a session's queue under the routed Agent's key (bridge/agent_bridge.py:1205-1207 -- "keep legacy token keys for the default agent, namespace the rest"), while cancel_session() and cancel_message() looked the queue up with the bare session id (channel/chat_channel.py:636, :666). For any Agent other than the default one -- a channel instance created with an agent_id in the console stamps bound_agent_id on every inbound message (app.py:193, agent/routing.py:57-78) -- the lookup missed, so #reset (plugins/godcmd/godcmd.py:340) left the queued messages in place to be processed after the memory was cleared, and recalling a queued Feishu message (channel/feishu/feishu_channel.py:697) still got answered. The futures half of cancel_session missed for the same reason, since consume() records futures under the queue key (:614-617).

What changed

channel/chat_channel.py -- both cancel paths now resolve the key the same way the enqueue path does:

• a new _queue_key(session_id, agent_id=None) goes through AgentBridge.scoped_session_key, the helper bridge/agent_bridge.py:673-684 already provides for exactly this ("cancel and steer lookups must be scoped"); if the bridge cannot be reached it falls back to the bare session id, the same way produce() falls back when routing fails, so a default-Agent install behaves byte-for-byte as before,
• cancel_session(session_id, agent_id=None) and cancel_message(session_id, message_id, agent_id=None) use it for self.sessions and self.futures.

plugins/godcmd/godcmd.py -- #reset passes e_context["context"].get("agent_id"), which is the value route_context() wrote onto the context on the way into the queue.

channel/feishu/feishu_channel.py -- _message_sessions records (session_id, agent_id) and is written after produce() has resolved the route, so a recall can rebuild the key; the two halves are passed to cancel_message. Reading context["agent_id"] before produce() would store the pre-routing value (or nothing), and a bound Agent that has since been disabled falls back to the default route inside produce() (agent/routing.py:71-77), so the value after the call is the only one that can match the key.

How it was verified

• Redone on the pristine tip 04eb97cf: with the queue filed under team-a::web:u1 -- which is what produce() does, pinned by its own test case -- cancel_session("web:u1") left qsize() == 1, and cancel_message("web:u1", ...) reported queued=0 while the message stayed in the queue. Running the two test files as submitted against that pristine checkout gives 10 failed, 10 passed; on this branch the same two files give 20 passed (adding tests/test_robustness_fixes.py, which already covers the default-Agent path, gives 25 passed).
• Whole suite, same tip, twice (pytest tests/ -q): pristine master 32 failed, 2285 passed; this branch 32 failed, 2294 passed. The FAILED lines are the same set in both runs (diff of the sorted lists is empty), so nothing regressed -- those are pre-existing environment-dependent failures on this Windows host, not caused by this diff. The nine extra passes are the new cases.
• ruff check channel/chat_channel.py channel/feishu/feishu_channel.py plugins/godcmd/godcmd.py tests/test_cancel_session_agent_scope.py tests/test_feishu_message_recall.py --select F --ignore F403,F405 -- clean.