Fix #1: Move _buildCompletions.TryRemove into finally block in
TestableBuildQueueSubscriber so cancelled/failed builds clean up
their TCS entries, preventing stale entries on resource restart.

Fix #3: Add MissingBuildInfoAnnotation_SkipsBuildAndReleasesQueue
test that uses the real MauiBuildQueueEventSubscriber to verify the
RunBuildAsync warning-and-skip path when MauiBuildInfoAnnotation is
absent, and confirms the semaphore is properly released.

Fix #5: Remove IDisposable from MauiBuildQueueAnnotation — no other
annotation in Aspire implements IDisposable and the semaphore is
garbage-collected on app shutdown. Remove the Dispose test.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>