fix(orchestrator): stop auditor alert-spawn rotation — ack as auditor on dispatch

The auditor respawned every ~3 min on the same stale rework alerts.

Root cause: _dispatch_audit_work's alert path fetched the SYSTEM-wide
"not fully acked" view (list_system_notifications), but the auditor is
read-only (no ack verb) and auditor_triage never acks — so once an alert
existed the CEO was the only party who could clear it, and the CEO hadn't
acked. The per-alert cooldown (PR #499) only paced a rotation through the
N un-acked alerts; it was a damper, not a fix.

Fix: fetch the auditor's OWN pending-ack view (GET /notifications authed
as the auditor -> list_for_agent, which filters acked_by for the auditor)
and ack the alert as the auditor on dispatch. Each alert is now a
one-shot, DB-persistent: the next tick cannot respawn on an alert the
auditor already observed — even one the CEO hasn't acked. Authed as the
auditor (not the system identity) so the route selects the per-recipient
view; HTTP rather than DB-direct so it shares the orchestrator's loop in
prod and stays loop-safe in the e2e harness (which runs _dispatch_audit_work
in its own asyncio.run loop, away from the app's DB engine).

e2e now asserts the alert is in acked_by for the auditor after dispatch —
the rotation-stopper itself, not just the spawn.

tests/e2e_smoke/test_auditor_triggers.py

@@ -228,3 +228,30 @@ def test_reactive_alert_producer_spawns_auditor(
     prompt = call.kwargs["initial_prompt"]
     assert "QUALITY ALERT" in prompt
     assert "missing edge-case coverage" in prompt
+
+    # Rotation-stopper: dispatch acks the alert as the auditor (the auditor is
+    # read-only, no ack verb), so the auditor's pending-ack view no longer
+    # returns it and the next tick cannot respawn on this same alert. Without
+    # this ack the per-alert cooldown only paced a rotation through every
+    # stale not-fully-acked alert — the loop being fixed.
+    async def _acked_by_auditor(session: AsyncSession) -> bool:
+        from roboco.db.tables import NotificationTable
+        from sqlalchemy import select
+
+        row = (
+            (
+                await session.execute(
+                    select(NotificationTable).where(
+                        NotificationTable.related_task_id == task_id,
+                        NotificationTable.type == NotificationType.ALERT,
+                    )
+                )
+            )
+            .scalars()
+            .one()
+        )
+        return auditor_id in row.acked_by
+
+    assert stack.run_db(_acked_by_auditor), (
+        "alert not acked as auditor after dispatch — rotation not stopped"
+    )