New source-agnostic SegmentedToggle primitive (rounded-full pill track, one
active option, aria-pressed drives the paint via the .pill recipe). Migrates
the three hand-rolled MATCH segments onto it:
- feed tag any/all "Match" toggle (Sidebar)
- feed Mine/Library scope bar (Sidebar; fullWidth + icons + per-option tips)
- Plex any/all combine toggle (PlexSidebar MatchToggle is now a thin binding)
Caption mode (justify-between + label) covers the match toggles; fullWidth
+ size="md" covers the scope bar. Adds SegmentedToggle.dom.test.tsx (6 tests).
Part of the app-wide single-select control unification; branch not merged.