Session removal can exceed its 15 s cleanup deadline on the Windows net472 leg (GetLogAsync cursor-past-tail test) #466

What failed

Merge-group run 39064994407 (#461 on 77bb1b5), job Build & Test (Windows), OpenCode.Sdk.Tests on net472: one failure out of 2,847.

failed GetLogAsync_Should_Answer_A_Cursor_Past_The_Tail_With_The_Marker_Alone (15s 466ms)
TUnit.Engine.Exceptions.TestFailedException: [Test Failure] TimeoutException:
Owned operation 'session removal' exceeded its cleanup deadline of 00:00:15.

The test passed on the same commit in #461's own PR CI and on every other leg. #461 changes only launcher contract tests and does not touch the session log or session cleanup. This looks like an intermittent cleanup-deadline timeout in the server-backed test harness on the Windows net472 leg.

What is needed

• Find out why session removal can exceed the 15 s owned-operation cleanup deadline on Windows net472: a slow runner, a server-side delete waiting on something, or a harness ordering problem. Fix the root cause. Widening the deadline or retrying is not a fix.
• The test name is also stale (GetLogAsync; the method is ReadLogAsync). TST-E4's stale-name step covers that, so it is not part of this issue.

Owner: Runtime lane. Recorded before re-enqueuing #461, as the merge-queue rule requires.