Introduce the one sort control every content surface will share:
- columnSort.ts gains the SortOption vocabulary + pure pickSort/healSort/
hydrateSort helpers (direction lives in SortState, never in the key).
- SortControl.tsx: the generic dropdown + asc/desc toggle, with an optional
"no sort" choice (tables) and a trailing adornment slot (the feed's reshuffle).
- ColumnSortControl is now a thin wrapper over SortControl (API unchanged, so
Channels + ChannelDiscovery are untouched); optionsFromColumns moved to
lib/sortOptions.ts to keep the component file fast-refresh clean.
- useSortState.ts: the per-account persist/hydrate/heal plumbing the channel
manager and discovery each hand-rolled, ready to replace both.
Pure logic is fully unit-tested (columnSort.test.ts 10 -> 23). Gate green:
tsc/eslint/prettier clean, vitest 93 pass. Feed/Plex/channels migration follows.
