The Cmd-K "Install theme…" palette listed Marketplace themes with no hint
that you already had them, and clicking one re-downloaded + re-installed a
theme you owned. The Appearance settings grid already detected this, but by
parsing theme descriptions inline on every render — plumbing that never made
it to the palette.
Lift it into one reactive source and reuse it everywhere:
- $marketplaceInstalls (computed over $userThemes): extensionId -> installed
theme, derived once via marketplaceIdOf and memoized, instead of rebuilding
a Set per render.
- Both install surfaces now mark owned rows installed and, on click,
re-activate the installed theme rather than re-fetching it.
- Drops the duplicated description-parsing in settings and the per-session
"installed here" state in both surfaces (the store is the source of truth,
so previously-installed themes show correctly too).
04639adace