When overriding a List attribute, render the shared AttributeListEditor
(whole-list replacement; element type fixed by the base, shown read-only via
ShowElementType=false) instead of the single-line input. Loading an existing
override decodes its JSON into rows (malformed -> empty); saving encodes rows to
canonical JSON with a pre-submit Decode round-trip guard surfacing element
errors inline. Clearing removes the InstanceAttributeOverride row
(repository-direct, mirroring native-alarm-source overrides). Non-List override
UX unchanged.
Joseph Doherty