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aligned, broken link fixed, StopToken deferral superseded in ADR-009.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/README.md

@@ -1,6 +1,6 @@
 ---
 status: draft
-last_updated: 2026-10-06 (ADR-018; OQ-11 resolved — question set closed)
+last_updated: 2026-10-06 (ADR-019/020 — second review round resolved)
 ---
 
 # alkstore — Architecture
@@ -53,6 +53,8 @@ pending architecture review and OQ resolution.
 | [016](decisions/016-deployment-honesty.md) | Deployment honesty — no runtime capability surface; compile-time engine identity + documented 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 category-tagged entries, five-step adoption discipline | Accepted |
+| [019](decisions/019-mechanism-handle-surfaces.md) | Mechanism-handle surfaces — handle traits (`Queue`/`StreamHandle`/`Outbox`/`Lock`/`JobHandle`), `Job`/`Schedule` shapes, `worker_id` identity, core `StopToken` | Accepted |
+| [020](decisions/020-enqueue-opt-semantics-and-bridges.md) | Enqueue-option semantics — delay/run_at precedence, relative `expires`, scheduler stamp source, serde_json payload encoding | Accepted |
 
 ## Open Questions
 
@@ -81,8 +83,10 @@ depth — [ADR-015](decisions/015-streams-depth.md)), ~~OQ-10~~
 (fork follow-through — provenance register + cherry-pick procedure,
 [ADR-018](decisions/018-provenance-register-and-cherry-picks.md)).
 
-No deferred OQs. With the question set closed, Phase 1 moves to
-architecture review closure and the implementation-phase gates.
+No deferred OQs. With the question set closed (and the 2026-10-06
+second review round resolving its findings directly as ADR-019/ADR-020
+rather than as new OQs), Phase 1 moves to architecture review closure
+and the implementation-phase gates.
 
 ## Document Lifecycle