decompose wave 5 — contract suite: audit-first split of the verification backlog (engines' columns already discharge most rows; map in review-wave-5's appendix), seven mechanism-grouped suite-row tasks (queue depth, scheduler, tx commit-atomicity, streams, locks, wakes, opts/backoff equivalence), two engine-side hardening tasks (sqlite commit-error arm, pg F-1 defense-in-depth), and the review-wave-5 gate that flips the engine specs to stable

tasks/pg-suite-infra-hardening.md

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+---
+id: pg-suite-infra-hardening
+name: Postgres test-infra hardening — F-1's defense-in-depth candidates
+status: pending
+depends_on: []
+scope: single
+risk: low
+impact: isolated
+level: implementation
+tags: [wave-5, postgres-engine, tests]
+---
+
+## Description
+
+Land the defense-in-depth test-infra hardening the wave-4 review
+recorded for F-1 (`tasks/review-wave-4.md` Notes) — **explicitly not
+load-bearing since `pg-fix-tx-wake` retired F-1's engine-side root
+cause** (the compose test is deterministic, 20/20 solo runs green at
+the fix-batch gate). This task exists because wave 5 was the named
+home ("wave 5's suite hardening, or a wave-5-adjacent test-infra
+task") and the candidates are cheap; if the wave-5 window gets tight,
+cancelling this task loses nothing but insurance.
+
+Work (the review's candidate dispositions, cheapest first):
+
+- **(a) Harden `must_recv_event`'s deadline** — replace the 20 ms
+  polling loop with a parked `recv().await` under a timeout wrapper;
+  the deadline assert still bounds the property, the poll-loop's
+  wake-subscription interaction surface goes away.
+- **(b) A `LOG_LAGGED`-style diagnostic counter on the bridge** —
+  discriminates "wake never arrived" from "wake arrived, re-drain
+  missed" if a wake-shaped flake ever recurs. Land only if it is a
+  small, honest addition (a test-observation counter, `#[cfg(test)]`-
+  gated or eprintln-postured per the house test style); skip and
+  record if it wants more machinery than that.
+
+Candidate (c) (leave the skip-posture as-is) is the do-nothing arm —
+adopted by default for anything not landed.
+
+## Acceptance Criteria
+
+- [ ] `must_recv_event` parks on `recv().await` under a timeout
+      wrapper (no polling loop); the pg stream tests stay green
+      against the harness server (a full stream-module run)
+- [ ] Candidate (b) either landed small or recorded as skipped with
+      the reason
+- [ ] `cargo test -p alkstore-postgres` green (server-less skips
+      clean); clippy `-D warnings`; fmt clean
+
+## References
+
+- tasks/review-wave-4.md (F-1's Notes — the candidate dispositions)
+- tasks/review-wave-4-fixes.md (F-1 retired; defense-in-depth posture)
+- tasks/pg-fix-tx-wake.md (the engine-side fix that made this
+  non-load-bearing)
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion