Placeholder AlarmStateChanged rows are a DebugView snapshot-only concept emitted
by InstanceActor.BuildAlarmStatesSnapshot; they are never a real alarm transition.
Their timestamp may be DateTimeOffset.MinValue (the Protobuf Timestamp lower boundary),
which can throw when packed via Timestamp.FromDateTimeOffset.
Added early-return guard at the top of HandleAlarmStateChanged before any timestamp
pack or channel write. Updated the existing NativeBindingLinkage round-trip test to
use a real (non-placeholder) native alarm; added DropsAlarmStateChanged_WhenIsConfiguredPlaceholder
to assert placeholders are silently dropped (15/15 pass).
Replace the two flat capped tables with a Bootstrap nav-tabs layout, each
tab hosting a TreeView<DebugTreeNode> built from the live latest-per-name
dictionaries via DebugTreeBuilder. Drop the MaxRows cap, auto-scroll locks,
and Clear buttons (change-feed affordances that don't fit a current-status
tree); HandleStreamEvent now does a plain dictionary upsert. Per-tab filters
ExpandAll on change so matches stay visible. Branch nodes surface roll-up
badges (active-count for alarms, bad-quality for attributes); native binding
nodes show active-count or 'no active conditions'. All existing badge helpers
and ValueFormatter reused. Marshalling/dispose/reconnect contract preserved
(SafeInvokeAsync/_disposed/Dispose unchanged; FilteredAttributeValues kept as
the render-thread dict reader the CentralUI-021 race test exercises).
Rework DebugViewAlarmTableTests for the tabbed-tree DOM: tab presence+default,
computed alarm grouped under its Motor1 branch with the active roll-up badge,
and a native condition nested under its source-binding node with the enriched
kind/severity/Unacked/Shelved badge set.
Computed alarms place as leaves at their path-qualified AlarmName; native conditions group under a deduped IsNativeBinding branch keyed by NativeSourceCanonicalName with condition children keyed canonical::sourceRef. Configured-placeholder events materialise a childless binding node. Alarm roll-up (WorstState/ActiveCount) excludes placeholders. Filter matches AlarmName/SourceReference/NativeSourceCanonicalName (OrdinalIgnoreCase) and retains ancestor + binding branches. 20 new TDD cases; 18 attribute cases stay green. No DebugTreeNode model changes.
Joseph Doherty