fix(watch): harden nudge/wake delivery across eviction, cancel, and identity rebinds

Wake path:
- Denial metacog nudge moves to the tool channel so it drains with the
  denied tool batch instead of the next user-message seam.
- wake_workstream_if_pending: shared wake gate for watch fires on
  already-idle workstreams (no IDLE transition for the watcher to
  observe), wired as wake_fn at every set_watch_runner site via the
  shared _watch_fire_wake_fn helper (closes over the Workstream OBJECT
  — after eviction+restore an id-keyed manager lookup would miss).
- session_worker exit backstop re-runs the wake gate the moment worker
  ownership clears: IDLE fans out on the worker thread, so
  transition-time wakes always landed on the reuse path and no-op'd
  (the coordinator idle_children strand).
- deliver_wake_nudge_from_queue contains GenerationCancelled — it is
  the wake worker's run() closure and only Exception is caught
  downstream.

Watch delivery:
- Terminal fires that cannot reach their workstream are HELD and
  redelivered on min(interval, 60s) without re-running the command,
  bounded by MAX_DELIVERY_ATTEMPTS per cycle and the watch's own
  max_polls across cycles; the poll charge commits durably at hold
  time so restarts stay budget-bounded.
- Restore admission control: per-ws dedup + MAX_CONCURRENT_RESTORES
  cap, presence-only re-check under the lock, detection-only stall
  alerts (reclaiming a wedged admission would trade capped degradation
  for total poll-pool collapse).
- Permanent-vs-transient restore taxonomy: corrupt persona stamp and
  genuinely-missing history (confirmed by a raising storage probe —
  the resume loader swallows read blips into []) deactivate the watch
  immediately; everything else holds and retries.
- Cancel-race defense: delivery paths re-check is_watch_active before
  stashing/dispatching, cancel paths write the row BEFORE
  forget_terminal_dispatched, the HTTP cancel endpoint clears runner
  state, and a per-tick sweep bounds the residual stash-after-clear
  interleaving to one check_interval.
- Abandon/exhaustion commits are write-then-clear so storage that can
  read but not write retries the row write instead of re-running the
  command every cycle; the fresh-fire unrestorable path stashes before
  its deactivation write for the same reason.

Registry follows identity:
- The dispatch registry is keyed by _ws_id at registration time; every
  rebind now moves it: non-fork resume() and /new go through
  _follow_watch_registration (new key live before the old is removed,
  never stealing a registration another live session holds), removals
  are owner-checked so tearing down a watch-restore shell or a
  resumed-away session cannot unregister a live pane, the restore
  shell yields to a registration that appears mid-restore, CLI
  --resume registers after the successful resume, and both the open
  path and the detail-GET lazy rehydrate wire the registration.

Teardown gating and backpressure honesty:
- cleanup_session_ui marks ws._closed FIRST under ws._lock — every
  teardown path (close, close_idle, evict, delete, discard) funnels
  through it — and session_worker.send re-checks under the same lock,
  so a wake can never spawn a worker on a torn-down workstream.
- Create responses carry initial_message_status when the initial
  message could not be delivered (queue_full / refused_closed) instead
  of reading as success; staged attachments survive for the retry;
  /send surfaces a closed workstream as 404 rather than queue_full.

Docs/spec: OpenAPI artifacts regenerated; api-reference documents the
new create-response field; TS SDK type extended.

Tests: ~30 new pins (cancel races, budget durability across restarts,
owner-checked registry moves, teardown gating, stall alerts,
backpressure surfaces, wait_until final re-check); wide subsystem
sweep green (2353 passed).

docs/api-reference.md

@@ -948,6 +948,7 @@ All fields are optional. The body can be empty or an empty JSON object.
 | `name`          | string | Auto-generated workstream name                      |
 | `resumed`       | bool   | Whether a previous session was successfully resumed |
 | `message_count` | int    | Number of messages in the resumed session (0 if fresh) |
+| `initial_message_status` | string | Present ONLY when the workstream was created but its `initial_message` could not be delivered: `"queue_full"` (a raced live worker's interjection queue was at capacity — resend via `/send`; any uploads stay staged) or `"refused_closed"` (the workstream was closed mid-create). Absent whenever the message was dispatched. |
 
 **Error (limit reached):**