Bug: Bug: Sibling breadcrumb dispatcher tests share the Task.Run distinct-thread assumption fixed in #900

[drmoisan]

• Work Mode: full-bug

Summary

Issue #900 fixed two tests that obtained a "worker thread" from Task.Run and asserted a
thread-identity property against it. Task.Run guarantees only a thread-pool thread, never a
different one, so under parallel execution the constructing thread can be the same pooled thread
and the guard under test is never exercised.

The same assumption remains in sibling tests that were out of #900's declared scope, including a
third test in the very file #900 modified, at line 332.

Environment

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Steps to Reproduce

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Expected Behavior

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Actual Behavior

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Logs / Screenshots

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Impact / Severity

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Source

From: docs/features/potential/2026-09-17-sibling-breadcrumb-dispatcher-tests-share-taskrun-assumption.md

[drmoisan]

Consolidated into #931 with #906, which shares the root cause: a test that depends on environment state it does not control. Verified still present at ItemViewerBreadcrumbThreadAffinityTests.cs:332, and five sibling files are listed for triage in #931. Closing in favour of #931.