Validate AddComment up-front (IsNullOrWhiteSpace guard + Warning log) so
a blank-comment command is cleanly rejected before reaching the engine
rather than faulting inside ApplyAddComment and being silently swallowed
by the outer catch. Mirrors the existing TimedShelve missing-UnshelveAtUtc
pattern.
Also fix two stale inline comments: the "async void crash" note on
TimedShelve now correctly says "fault escaping async Task → supervision
restart", and the ownership-filter now documents the benign race with a
concurrent LoadAsync clearing the loaded set.
Tests: AlarmCommand_add_comment_empty_text_is_rejected_not_driven (Theory
— empty string + whitespace) and AlarmCommand_add_comment_nonempty_drives_engine
(positive path, asserts CommentAdded transition on alerts topic).
Joseph Doherty
1d7e2a0f8b