feat(issue-5): auto-completion gate and durable pending notification

The gate does not re-decide anything. Phase 2a already decides, fail-closed and
against contract-pinned vectors; this supplies real evidence to that decision and
commits only if three independent gates agree: the global switch is on, the
backend has observed evidence that it reaches a quiescent state, and the job
itself opted in. Default is off.

The backend allowlist is evidence-based rather than optimistic. Inferring
"finished" from stillness requires stillness to have been observed, and only
three of six backends have that. An operator may narrow the list; a name that
was never observed is dropped rather than trusted, so it cannot be widened by
configuration.

Everything else holds. An unreadable manifest, a report rewritten after
finalization, missing evidence for a declared side effect, a policy that raises:
all refuse. "Could not decide" is never "done". A late explicit terminal wins,
because the boundary refuses the inferred one -- that is the boundary working,
not an error in the gate.

Notification intent is committed in the same atomic write as the state, so a
crash between committing and publishing leaves a record that still says the
world has not been told. Recovery re-sends; duplicates are already dropped by
sequence. A failed send deliberately leaves the intent pending, because an
unsent notification that looks sent is worse than one that is retried.

Two fixes this surfaced. Settling used a request that terminal records refuse,
which made an owed notification impossible to ever settle; settling is now a
status-free bookkeeping request, valid in any state. And the phase 2a guard
against shell references was matching hashlib.sha256 as a substring, so it now
requires a word boundary.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UrDNJkHmm18uu7n7JwV5Qd

.agents/skills/lib_py/delegation/notifier.py

@@ -0,0 +1,97 @@
+"""Durable notification intent, carried in the job record.
+
+The contract forbids a separate outbox store, so the intent rides in the record
+the transition already writes: one atomic commit records both the new state and
+the fact that the world has not been told yet. Publishing then happens outside
+the registry lock, and settling the intent is itself an ordinary transition.
+
+That ordering is the point. If the process dies between the commit and the
+publish, the record still says a notification is owed, and startup recovery
+re-sends it. Duplicates are safe: the subscriber already drops any event whose
+sequence is not greater than the highest it has accepted.
+"""
+from __future__ import annotations
+
+import logging
+from typing import Any, Dict, List, Optional
+
+from lib_py.delegation import mqtt_common
+
+logger = logging.getLogger("delegate_job.notifier")
+
+FIELD = "pending_notification"
+
+
+def intent_for(event: str, seq: int, timestamp: str, detail: str = "") -> Dict[str, Any]:
+    return {"event": event, "seq": seq, "timestamp": timestamp, "detail": detail}
+
+
+def pending(job_id: str, registry_dir: str) -> Optional[Dict[str, Any]]:
+    try:
+        return mqtt_common.load_job(job_id, registry_dir).get(FIELD)
+    except FileNotFoundError:
+        return None
+
+
+def jobs_with_pending(registry_dir: str) -> List[str]:
+    """Records still owing a notification. The input to restart recovery."""
+    from lib_py.delegation import registry  # local: keeps module import order flat
+
+    out = []
+    for record in registry.list_jobs(registry_dir):
+        if record.get(FIELD):
+            out.append(record["job_id"])
+    return out
+
+
+def settle(job_id: str, registry_dir: str, source: str = "notifier") -> bool:
+    """Clear the intent once the event is on the wire.
+
+    Goes through the transition boundary like every other record write, using a
+    request that carries no status: settling is about a terminal, so a request
+    the terminal state would refuse could never be used to settle one.
+    """
+    from lib_py.delegation import engine
+
+    result = engine.transition(job_id, "notification_settled", registry_dir=registry_dir,
+                               fields={FIELD: None}, source=source)
+    return result.committed
+
+
+def flush(job_id: str, registry_dir: str, publish=None, attempts: int = 3) -> bool:
+    """Publish an owed notification and settle it. Safe to call repeatedly.
+
+    Returns True when nothing is owed afterwards. A failure leaves the intent in
+    place on purpose: an unsent notification that looks sent is worse than one
+    that is retried.
+    """
+    intent = pending(job_id, registry_dir)
+    if not intent:
+        return True
+
+    if publish is None:
+        from lib_py.delegation import publish_event as _pe
+
+        def publish(job, intent_, registry_dir_):
+            return _pe.main(["--registry-dir", registry_dir_, "--job", job,
+                             "--event", intent_["event"], "--detail",
+                             intent_.get("detail", ""), "--attempts", str(attempts)])
+
+    try:
+        rc = publish(job_id, intent, registry_dir)
+    except Exception as exc:
+        logger.warning("notification publish failed for %s: %s", job_id, exc)
+        return False
+    if rc != 0:
+        logger.warning("notification for %s not accepted (rc=%s); leaving it pending",
+                       job_id, rc)
+        return False
+    return settle(job_id, registry_dir)
+
+
+def recover(registry_dir: str, publish=None) -> Dict[str, bool]:
+    """Re-send every owed notification. Called at startup after a crash."""
+    results = {}
+    for job_id in jobs_with_pending(registry_dir):
+        results[job_id] = flush(job_id, registry_dir, publish=publish)
+    return results