PresencePollingTests.aTickThatChangesNothingTellsNobody is flaky: probe.asked.count races the tick

[scgopi]

Fails intermittently, ~1 in 5, independent of any recent change:

✘ Test aTickThatChangesNothingTellsNobody() recorded an issue at PresencePollingTests.swift:120:5: Expectation failed: await probe.asked.count == 1
✘ Test run with 1672 tests in 175 suites failed after 63.602 seconds with 1 issue.

Evidence (same machine, same head, 2026-09-06):

Run	Result
Full suite, earlier	pass
Full suite, later	fail
Isolated ×5	1 fail / 4 pass

The failure is an async count expectation racing the tick (failed after 0.001 s), not an assertion about state that changed. Unrelated to #317's diff (reaper/workspace/persistence); flagging it because a flake that fails a full-suite gate costs every loop gating behind one.

Suggested direction: make the probe's ask observable (a continuation/confirmation expectation) rather than polling asked.count immediately after the tick.

[scgopi]

Closing as no longer reproducible. On the head of #321 (2fd3476, which carries every drain and presence change since this was filed), PresencePollingTests ran 30 iterations in isolation with -test-iterations 30 -run-tests-until-failure: 300/300 passed, aTickThatChangesNothingTellsNobody 30/30. The full 1692-test suite also passed on that head. No commit targeted this test specifically; if the count race comes back, reopen with the run.