ADR-014: transactional outbox enqueue — outbox_enqueue_tx on TxHandle (OQ-13 resolved)

docs/architecture/engine-postgres.md

@@ -109,6 +109,7 @@ the record in [ADR-003](decisions/003-sqlite-driver.md).
 | [009](decisions/009-scheduler-collapse.md) | Scheduler collapse | schedule rows in the engine schema, re-derived tick, row-locked fire tx, `__alkstore_scheduler` leadership |
 | [010](decisions/010-queue-semantics-depth.md) | Queue depth | job-stamped opts, equal-jitter backoff, dead-letter move, no-stranded-rows sweep, one engine-owned schema |
 | [012](decisions/012-forked-substrate-design.md) | Fork design | contract-blind substrate (SQLite side); pg engine owns its own curve/stamps arithmetic, equivalence pinned by the contract suite |
+| [014](decisions/014-outbox-tx-enqueue.md) | Outbox tx enqueue | `outbox_enqueue_tx` on `TxHandle`; derivation engine-side inside the caller's tx |
 
 ## Open Questions
 
@@ -121,8 +122,12 @@ questions affecting this document:
 - **OQ-12**: streams depth (affects this engine's stream realization
   — event-shape/ordering/retention equivalents on the pg side)
   ([open](open-questions.md))
-- **OQ-13**: transactional outbox enqueue shape (affects this
-  engine's `TxHandle` impl) ([open](open-questions.md))
+- **OQ-13**: transactional outbox enqueue shape — **resolved**
+  (2026-10-05, [ADR-014](decisions/014-outbox-tx-enqueue.md)):
+  `outbox_enqueue_tx(outbox, opts, payload)` on the `TxHandle` trait;
+  the pg engine validates the outbox name and derives
+  `__alkstore_outbox:{name}` engine-side inside the caller's
+  transaction.
 
 Resolved: **OQ-09** (scheduler collapse —
 [ADR-009](decisions/009-scheduler-collapse.md)) and **OQ-05** (queue