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).
Subscribe the host to the cluster alarm-commands DPS topic in PreStart and
drive the matching ScriptedAlarmEngine op per inbound AlarmCommand. An
ownership filter (engine.LoadedAlarmIds) ignores commands for alarms this
node does not own; TimedShelve without UnshelveAtUtc and unknown operations
are logged + rejected (never thrown); op failures are caught + logged so a
faulting op can't fault the actor. Re-projection is left to the engine's
existing OnEvent -> OnEngineEmission path.
Handler is a Task-returning ReceiveAsync (the project's AK2003 analyzer
forbids an async-void Receive delegate), giving ordered awaited async on the
actor thread. Adds 3 TestKit tests: ack drives the engine with mapped args,
unowned command ignored, missing-UnshelveAtUtc TimedShelve rejected not
thrown.
Joseph Doherty