Dispose the wave-6 class-1-window observations (release-contract-window-close)

The pre-release pass's last contract-text dispositions, each dated
in-place citing the 2026-10-11 close-out pass (ADR-017 §2's terminal
window):

- Publish→wake ordering tolerance: documented tolerance (decided with
  the user) — core-contract.md streams paragraph + delivery-obligations
  bullet, ADR-015 §4 companion annotation; the wake = offset-order
  ADR amendment declined (commit-ordered pg visibility; hint-shaped
  wake posture).
- ADR-023 §2: heartbeat(extend) and save_offset(offset) join the
  boundary/offset row (total — negatives well-defined), with the
  home rationale annotated; core-contract's domain paragraph
  mirrors; the backlog numeric-domain row registers the suite-duty
  follow-up.
- ADR-021 §5: EventReceiver::try_recv's closed shape pinned
  (Err(Closed), mirroring ADR-008 §3); core-contract subscribe arms
  sentence extended.
- get_job prose: core-contract queues section + queues.md's reads
  sentence now say the uniform id-global / get_job_tx-filtered split.
- Mem-arithmetic observation: no-action disposition recorded in the
  task Notes (byte-level transplants; equivalence suite-pinned
  three-way).

Suite stamps checked — no accumulation required (no cited § text
changed meaning). Docs-only; gates green: build, workspace tests,
clippy -D warnings, fmt, fuzz replay, rustdoc -D warnings,
taskgraph validate (79 tasks).

docs/architecture/decisions/021-tx-reads-and-value-shape-fixes.md

@@ -258,6 +258,20 @@ The pinned shape's unpinned arms:
   absent-consumer = 0 rule,
   [ADR-019](019-mechanism-handle-surfaces.md) §1, already defines
   the pre-save state).
+- *(Annotation, 2026-10-11 — the pre-release class-1 close-out pass
+  ([ADR-017](017-contract-versioning.md) §2), disposing the wave-6
+  review gate's recorded unpinned shape: **`EventReceiver::try_recv`'s
+  closed shape is `Err(Closed)`.** §5 pinned only `recv()`'s arms;
+  the poll form's arms are the same taxonomy applied without the
+  wait — `Ok(None)` = no event pending right now (idle), `Err(Closed)`
+  = the receiver closed (terminal — the same causes the `None` arm
+  documents, engine asymmetry included), and the rest of the `Err`
+  arm carries `Database` only, exactly like `recv()`. The shape
+  mirrors `WakeReceiver::try_recv`
+  ([ADR-008](008-contract-v1-pinning.md) §3, where closed and idle are
+  distinguishable states by the same construction) and is uniform on
+  all three engines; core's rustdoc pinned it from landing, and the
+  mem engine's suite pins it in test.)*
 
 ## Consequences