Show constructor names in family-view data fam-instance rows too

Show constructor names in family-view data fam-instance rows too

The family view (drilling into a family directly) had its own
fam-instance label code path that bypassed renderFamInstHead, so
data fam-instance rows showed only their args (no constructor
names). Mirror the renderFamInstHead behaviour: append `= ConA |
ConB` for data fam-instances. The family name itself stays implicit
(it's already at the top of the family view).

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