The test tree holds zero hand-woven concurrency gates, and the allow file is gone

A hand-woven gate — ManualResetEventSlim and its relatives — parks a thread until somebody signals it. In product code that thread is a hub action block or a grain turn, and the deadlock is immediate. In a test the same primitive fails more quietly: when an assertion throws before the release runs, the worker it deliberately blocked stays blocked for its full bound and bleeds into the next test. That is not hypothetical — one such site held a pool thread for two minutes and made an unrelated test fail.

The ratchet added a day earlier froze that debt at a measured 79 sites across 23 files, every one a ManualResetEventSlim, 32 of them in IoPoolTest.cs. All 79 are now converted, and test/HandWovenGateSites.allow is deleted.

Two shapes replaced them, chosen by which way the signal travels:

• Producer → test (a handler reporting that it started, a pooled leaf, a .Finally, a disposal callback) becomes an AsyncSubject<Unit> the producer completes, awaited through the house assertion helpers — await x.Should().Within(...).Emit(because), or NotEmit(within) for the negative case. That suspends the test instead of parking its thread, so it cannot self-deadlock and cannot strand anything.
• Test → a worker it deliberately parks — a wedged action block, a leaf that ignores its cancellation token, a merge turn held open so an ack provably cannot arrive — keeps the park, because the park is the subject, but drops the kernel handle: the worker polls a volatile flag under a bounded SpinWait.SpinUntil, and the release is written in a finally so a failing assertion can never leave it held.

No assertion was weakened and no timeout widened; several tests gained a try/finally they did not have. test now sits in the guard's zero-tolerance roots alongside src/, tools/, samples/, clients/ and memex/, held at zero with no allow file anywhere — and a new check fails if the deleted one ever comes back. The full account of the two shapes, the traps, and what the sweep measured is in Removing Hand-Woven Concurrency Gates.