- collections: the resync-failed-after-successful-write path now returns 422
(honest "reconcile on next sync" detail), NOT 502. The frontend treats
502/503/504 as gateway-unreachable and raises a sticky offline banner
(api/core.ts RETRIABLE_GATEWAY); the app answered, so a 422 action-error
toast is correct. Removes the false-offline regression the 502 introduced,
and — since 422 isn't retried — the create double-write vector with it.
- tests: make the mutate-then-resync rollback assertion non-vacuous — the
resync stub now flushes a partial local change before raising, so the test
proves db.rollback() actually undoes it; split into a write-failed (422)
case and a resync-failed (422 + reconcile detail + rollback) case.
- New-collection dup hint is now muted-tone with its own nameMaybeTaken copy
(per-library uniqueness means the name may be free here) instead of the red
authoritative nameTaken, which the still-enabled create flow contradicts.
- history: cover the navCounter post-reload collision guard (ensureNavId
advances the counter past a higher persisted sfScroll id).
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