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aligned, broken link fixed, StopToken deferral superseded in ADR-009.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

@@ -1,6 +1,6 @@
 ---
 status: draft
-last_updated: 2026-10-06 (OQ-11 resolved — ADR-018)
+last_updated: 2026-10-06 (ADR-019/020 — handle surfaces, enqueue semantics)
 ---
 
 # SQLite engine
@@ -133,6 +133,8 @@ family is `__alkstore_*` (ADR-010 §8's naming authorization).
 | [016](decisions/016-deployment-honesty.md) | Deployment honesty | no runtime capability surface; single-host posture stated by crate identity + docs; this engine never produces `PayloadTooLarge` (pinned in the contract suite) |
 | [017](decisions/017-contract-versioning.md) | Contract versioning | engine pins core `alkstore = "1.y"` in its manifest; substrate cherry-picks are class-4 non-events; adoption duties per its §5 |
 | [018](decisions/018-provenance-register-and-cherry-picks.md) | Substrate provenance | `src/substrate/PROVENANCE.md` (identity, delta register — cherry-picks as tagged entries); cherry-picks recorded at adoption, non-versioning |
+| [019](decisions/019-mechanism-handle-surfaces.md) | Handle surfaces | boxed handle traits (`Queue`/`StreamHandle`/`Outbox`/`Lock`/`JobHandle`); `worker_id` stamps the row's claimant column; `StopToken` core-owned |
+| [020](decisions/020-enqueue-opt-semantics-and-bridges.md) | Enqueue options | delay-over-`run_at` in the substrate's re-derived enqueue; scheduler fires stamp from derived defaults; serde_json byte encoding |
 
 ## Open Questions