Get Extension Events

Poll for extension lifecycle events the current user has triggered.<br><br>Events are scoped to the authenticated user via a server-derived keyspace<br>(user:{user_id}); there is no client-controllable keyspace, so an<br>authenticated user cannot read another user's flow-migration or<br>bundle-reload events. A client-supplied keyspace query parameter is<br>rejected with 422 so the contract is explicit -- previously the value was<br>silently dropped, which masked client bugs that assumed it had effect.<br><br>svc.since() uses blocking sqlite3; run in a thread pool so the asyncio<br>event loop is not held while waiting on disk I/O.