suite: async past_stamp_sleep for current-thread flavor readiness

Replace the harness's blocking std::thread::sleep with tokio::time::sleep
across all nine call sites, note the no-blocking-calls-inside-rows posture
in the helper's doc comment, and mark the task completed. Both engines'
contract suites re-run green with assertions and tolerances unchanged
(ADR-024 \u00a75 item 4).

tasks/suite-harness-current-thread.md

@@ -1,7 +1,7 @@
 ---
 id: suite-harness-current-thread
 name: Contract-suite harness — async sleep in `past_stamp_sleep`, current-thread flavor readiness
-status: pending
+status: completed
 depends_on: []
 scope: narrow
 risk: low
@@ -38,12 +38,12 @@ This task is engine-independent and can run any time before
 
 ## Acceptance Criteria
 
-- [ ] `past_stamp_sleep` is async (`tokio::time::sleep`)
-- [ ] Both engines' existing suites re-run green with identical
+- [x] `past_stamp_sleep` is async (`tokio::time::sleep`)
+- [x] Both engines' existing suites re-run green with identical
       assertions and tolerances (determinism posture intact)
-- [ ] The no-blocking-calls posture noted where the harness's
+- [x] The no-blocking-calls posture noted where the harness's
       determinism posture is documented
-- [ ] Clippy `-D warnings`, fmt clean; workspace gates green
+- [x] Clippy `-D warnings`, fmt clean; workspace gates green
 
 ## References
 
@@ -55,8 +55,28 @@ This task is engine-independent and can run any time before
 
 ## Notes
 
-> To be filled by implementation agent
+- The posture note went into `past_stamp_sleep`'s doc comment rather
+  than the factory contract notes: the posture is a harness rule about
+  row internals (what a row may call), not part of the
+  `StoreFactory` shape, and the doc comment sits exactly where a row
+  author reaches for a sleep. The comment cites ADR-024 §5 for the
+  current-thread flavor that enforces it.
+- Five rows exercise the helper across its two use shapes (the
+  lapse-settle legs and the scheduler runner-less-pause leg):
+  `lock_ttl_expiry_and_reacquisition`, `job_handle_validity_predicate`,
+  `queue_depth_reclaim_and_dead_letter`, `sweep_no_stranded_rows`,
+  `scheduler_bounded_catchup`. All nine call sites gained `.await`;
+  assertions and tolerances untouched.
 
 ## Summary
 
-> To be filled on completion
+`past_stamp_sleep` now awaits `tokio::time::sleep` instead of blocking
+on `std::thread::sleep` (alkstore-contract-suite/src/properties.rs),
+making every suite row current-thread-safe for the mem engine's
+`#[tokio::test(flavor = "current_thread")]` column (ADR-024 §5 item 4);
+the doc comment records the no-blocking-calls-inside-rows posture.
+Both engines' `contract_suite` re-ran fully green (25/25 each, SQLite
+15.0 s / Postgres 21.3 s — no timing drift, tolerances unchanged); the
+full workspace build, tests, `clippy -D warnings`, and `fmt --check`
+pass. PostgreSQL leg ran against the POC container (`pglo-poc`, port
+15432, creds per docs/reviews/003 §env note).