ADR-019/020: second review round — handle surfaces, enqueue semantics, payload bridge + mechanical fixes

ADR-019: mechanism-handle traits pinned (Queue/StreamHandle/Outbox/
Lock/JobHandle), Job/Schedule struct shapes, worker_id claimant
identity, core StopToken — closes the 'pin at implementation' residue
before ADR-017's amend-in-place window terminates at first release.

ADR-020: delay-wins-over-run_at precedence (honker parity), relative
expires, scheduler-fired stamps from derived queue defaults, serde_json
byte-level payload encoding.

Mechanical: overview/engine-postgres ADR tables completed through 020,
core-contract Errors section re-framed to class-1, ADR-014 sketch
annotated with publish_with_key_tx, ADR-015 status dated, reserved-
namespace kinds list normalized to six kinds, redrive gate wording
aligned, broken link fixed, StopToken deferral superseded in ADR-009.

docs/architecture/deployment.md

@@ -1,6 +1,6 @@
 ---
 status: draft
-last_updated: 2026-10-06
+last_updated: 2026-10-06 (ADR-019/020 — handle surfaces, enqueue semantics, payload bridge)
 ---
 
 # Deployment