HTTP bridge: aborted completed-event bookkeeping leaks API-key reservation heartbeat

[Soju06]

Summary

When HTTP bridge completed-event bookkeeping aborts (raises or is cancelled) after the terminal request has been popped from session.pending_requests, the request's API-key reservation heartbeat is never cancelled and the reservation is never released.

Details

Ordering (observable on main; surfaced while reviewing #1527 but not introduced by it):

1. response.completed processing pops the terminal request from session.pending_requests under pending_lock and proceeds to continuity/settlement bookkeeping.
2. Bookkeeping raises or is cancelled before finalization.
3. The downstream stream eventually times out and its finally calls _detach_http_bridge_request.
4. In _detach_http_bridge_request, the request is no longer in session.pending_requests, so detached stays False and the function returns before reaching:
   • self._cancel_request_state_api_key_reservation_heartbeat(request_state)
   • await self._release_websocket_request_state_reservation(request_state)
5. The reservation heartbeat loop (while not stop_event.is_set(): ...) keeps touching the reservation indefinitely, retaining quota and generating repeated database writes.

The error-path regression added in #1527 (test_http_bridge_stream_waits_only_while_completed_delivery_is_active[error]) proves the client-facing fallback (response.failed + idle timeout), but does not assert reservation settlement — the leak is invisible to that test.

Expected

A request whose completed bookkeeping aborts after the pending pop must still be settled exactly once: heartbeat cancelled, API-key reservation released, and state finalized or restored to an ownership that cleanup can reach.

Notes

• Related: fix(proxy): preserve terminal delivery across detach #1527 (review comment item 2).
• Candidate direction: on abort after the claim, either restore the request to a cleanup-reachable state or run the reservation settlement path directly in the abort handler; regression should assert heartbeat cancellation and reservation release on the abort path.