fix(service): validate subagent HITL confirm against worker SSOT and cascade interrupt

[REISEN2330]

Fixes #2324

What

Two guards around the subagent HITL confirm loop:

1. POST /chat's confirm-routing branch now checks the worker's SSOT
   (_worker_still_asking) before enqueueing the resume. When the worker
   is no longer parked on the ASKING tool call, the stale card is cleared
   (projection delete + subagent_user_confirm_result publish) and the
   endpoint returns 409 — so the front-end stops re-posting the same
   UserConfirmResultEvent (previously 437x) instead of spinning forever.
2. POST /sessions/{id}/interrupt now cascades to team members: parked
   HITL runs are interrupted via resume triggers carrying
   UserInterruptEvent, and their projected cards are purged, so the
   card can no longer survive an interrupt.

Verification

• pre-commit run --all-files clean
• pytest tests/chat_router_hitl_test.py -v — 3 new regression tests pass
• pytest tests/hitl_user_confirmation_test.py tests/service_subagent_hitl_projector_test.py -q — 16 pass