- PaginatedCardGridTabState: the collections and playlists tabs were 95%
identical; they now supply only pageSize/fetchPage/idOf instead of each
duplicating the grid, memo, inflation budget and focus wiring.
- EtagCachedRemoteStore: the anime-lists and fribb mapping stores now share
one download/cache/isolate-parse/conditional-GET lifecycle.
- FocusableTileStateMixin manages its own initState/didUpdateWidget/dispose
instead of requiring every caller to forward three lifecycle hooks.
Also drops unused ServerCapabilities entries and dead code in
focusable_list_tile and music/track_row.
The aired-order rework can sweep correctly-placed Specials into "download
next N"; this toggle lets users opt out. Shown only for whole shows
(reusing FocusableSwitchListTile via an optional toggle on the shared
option-picker dialog), remembered across opens via a BoolPref
(default on = unchanged behavior). Filters Specials at the single
collect choke point (_collectPlayable), with a guard so explicitly
downloading the Specials season still queues its episodes.
edde746