The remaining E4 deep-review deferred gaps, in one sprint:
- readSelectedId split into playlistsInit.ts (react-refresh-clean, testable) —
?pl accepted only as a positive integer; empty/0/negative/fractional/non-numeric
fall back to the stored selection; null when neither is present.
- useUrlMirror: mounts write the param, a same-serialized rerender does NOT
re-fire (stable dep), a null value clears the key, other params preserved.
- usePref: a pending debounced write is FLUSHED on unmount (not dropped); an
unmount with nothing pending stays silent.
20 new test cases; full FE gate green (tsc/eslint/prettier/knip, 309 vitest).
Fold the hand-rolled server-pref plumbing (savePrefs + local mirror + me-cache
merge + adopt-on-login) into a single usePref<T>(serverKey, default, opts) hook,
plus useSavePref for dynamic multi-key patches.
Migrated (6 savePrefs call sites + 2 duplicated adopt effects -> the hook):
- FeedViewProvider: view
- App: filterCollapsed, playlistsCollapsed (+ their adopt block removed)
- PlayerModal: playerAutoAdvance, playerLoop
- plexDetailUi: plexInfoArtBg/Cast/Related (savePref via useSavePref)
Left as-is by design: panel layouts (a dynamically-indexed Record, not one key),
language (i18n store, no React state), PrefsProvider (debounced multi-field
auto-save + baseline echo-suppression - a different model).
Behaviour-equivalent (net -84 LOC at the call sites). usePref.dom.test covers
the three seed sources, persist path, debounce, adopt, parse, and useSavePref.
Frontend gate green: typecheck, knip, eslint (0 err), prettier, 238 vitest.
peter