The app scrolls one persistent <main> (PageScroller); its saved offsets were keyed by a
content `scrollKey` that is the same for a Plex page's Discover and grid views, so opening
a Browse-by-genre tile inherited the scrolled-down Discover offset (landing mid-page) and
Back couldn't tell the two views apart.
Tie scroll memory to the history entry instead: every pushState that opens a main-content
view stamps a fresh `sfScroll` id into history.state (setPage, Plex sub-view open); the
initial/legacy entries get one lazily via replaceState. PageScroller now saves/restores per
`${entryId}:${scrollKey}` — the entry id makes Back restore exactly where you left an entry
and a forward navigation (new id) open at the top, while the scrollKey still resets a new
feed filter to the top within the same entry. A small nav bus lets a Plex sub-view open
(which doesn't re-render the scroller) trigger the restore; `history.scrollRestoration` is
set to manual since the browser can't see our inner scroller.
Verified live: genre tile opens the grid at the top and Back returns to the Discover scroll;
feed→plex→Back restores the feed scroll; a feed filter change still resets to the top.
Gate: tsc/lint/knip/prettier clean, 5 new nav-id unit tests, full vitest green.
peter
1e5232f47a