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).
peter
d2f2085f1f