ADR-021: third review round — tx-read methods, Job.claimed_at, schedule() queue validation, drop=rollback, receiver arms

docs/architecture/decisions/014-outbox-tx-enqueue.md

@@ -179,7 +179,12 @@ smallest surface that restores the property.
   documentation must state plainly: **there is no way to enqueue into
   the backing queue except through the outbox surface** (auto-commit
   `outbox.enqueue` or tx `outbox_enqueue_tx`) — itself the guarantee
-  that the derivation cannot be collided with.
+  that the derivation cannot be collided with. *(Guarantee completed
+  2026-10-07 by [ADR-021](021-tx-reads-and-value-shape-fixes.md) §3:
+  `schedule()`'s queue argument now rejects the reserved prefix too —
+  without that pin, a schedule row storing `__alkstore_outbox:{name}`
+  as its fire target would have been a third write path into the
+  backing queue.)*
 
 ## References