Render external type families as grey diamonds in the classes view

Render external type families as grey diamonds in the classes view

External-ref stubs in the classes view all defaulted to kind:
"class", so external families like SigDSIGN / HeaderHash / SignKeyKES
showed as grey rounded-rectangles instead of the grey diamonds the
external-family styling expects. We DO know which refs are families
when they came from a FamilyApp use site (collectFamilyAppsInArgs)
or an associated-type list (ciAssocTypes); collect those qids and
tag their external nodes with kind: "family". Bare superclass refs
still default to "class" — same case as before for Show / Typeable /
NoThunks shaped externals.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>