Documents lessons from building pi Zulip extension and Hermes Zulip plugin:
1. Queue registration content-type
2. Missing bot_user_id for @mentions
3. Zero stream subscriptions
4. Stale errors never cleared
5. Stuck detection too aggressive
6. Env var name mismatch
7. Poll interval too aggressive
8. A2A port conflict
Also: fixed Hermes adapter to clear stale errors on successful poll
