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aligned, broken link fixed, StopToken deferral superseded in ADR-009.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/overview.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)
 ---
 
 # alkstore — Overview
@@ -80,6 +80,10 @@ Per [ADR-002](decisions/002-feature-scope.md):
 | [014](decisions/014-outbox-tx-enqueue.md) | Transactional outbox enqueue (`outbox_enqueue_tx` on `TxHandle`) | Accepted |
 | [015](decisions/015-streams-depth.md) | Streams depth (carried-metadata keys, global-FIFO ordering, `StreamEvent`, `trim_to`) | Accepted |
 | [016](decisions/016-deployment-honesty.md) | Deployment honesty (no runtime capability surface; compile-time identity + matrix) | Accepted |
+| [017](decisions/017-contract-versioning.md) | Contract versioning (core crate's semver is the contract version; change classes, pairing carriers, lockstep duties) | Accepted |
+| [018](decisions/018-provenance-register-and-cherry-picks.md) | Substrate provenance register and cherry-pick procedure (`PROVENANCE.md` in-tree, per-delta entries) | Accepted |
+| [019](decisions/019-mechanism-handle-surfaces.md) | Mechanism-handle surfaces (handle traits, `Job`/`Schedule` shapes, `worker_id`, `StopToken`) | Accepted |
+| [020](decisions/020-enqueue-opt-semantics-and-bridges.md) | Enqueue-option semantics (delay/run_at, expires, scheduler stamp source, payload encoding) | Accepted |
 
 ## Non-goals