The shell owns the scroller, so it owns the scroll policy. PageScroller
now takes a scrollKey identifying the logical view and keeps a per-view
offset in a module-level map, recorded live on scroll:
- same key returning (feed -> channel -> Back, filters unchanged) restores
where you were (bug 1) -- the feed's scroller unmounts, but the saved
offset survives and is re-applied, retried over a few frames so the
virtualized list has time to reach its full height;
- a new key (feed filters changed) starts at the top of the fresh result
set (bug 3). q is normalised out of the feed key so typing doesn't reset.
Recording on scroll rather than at unmount matters: by cleanup time the
scroller's scrollTop is already zeroed, so a cleanup-read saved 0.
Also fixes a Maximum-update-depth loop this introduced: the combined
element/fade ref was an inline callback, so React re-attached it every
commit and re-ran useScrollFade's state setter. Bound it with useCallback.
Adds E2E locks for bugs 1, 3 and 4 (restore on Back, reset on filter,
toolbar stays pinned). Full suite 14/14 green on :5173; tsc + knip clean.
Locks the five flows the refactor must not break (feed, channel, player,
settings, nav) so later sprints can prove they changed nothing. Adds a thin
data-testid layer and a dedicated seeded non-demo account; the suite runs on
the baked :8080 stack (authoritative) or :5173. No product-behaviour change.
peter