Adds a reusable FilterSelect: a "Label: value ▾" pill that opens a listbox (a checkmark
row for single-select, a checkbox row for multi), on the AnchoredPopover platform. It
replaces the two feed-toolbar chip walls:
- Watch state (single-select, default All) — picking a row replaces + closes.
- Content types (multi-select, default Normal; requireOne keeps at least one on) — rows
toggle and the panel stays open.
The trigger summarises multi picks as "First +N". The component is source-agnostic, meant
for reuse anywhere a small known option set currently renders as a chip group.
FilterSelect takes a `testId` → the trigger gets it, each option gets `${testId}-${value}`,
so the feed/channel E2Es keep stable selectors. They now open the dropdown and assert the
option's aria-selected instead of the old inline aria-pressed chips (new expectContentType/
toggleContentType helpers).
The "Back restores the feed scroll position" spec failed against the production
build while the app was in fact correct. Root cause, found by instrumenting
PageScroller and comparing the baked :8080 build to live :5173:
`getByTestId("video-card-channel").first()` grabs the first card in the DOM, which
after scrolling 3000px is in the virtualizer's overscan ABOVE the viewport.
Playwright scrolls it into view to click it, moving the feed from 2879 to ~1017–1253
BEFORE navigating; PageScroller's save-on-scroll records that moved position, so Back
faithfully restores the moved position — under the test's own tolerance. A real user
clicks a card they can see, which does not move the feed.
New helper clickVisibleChannelLink() clicks a card whose bounding box is inside the
viewport. Restore now lands at ~2804 (was ~1017). 17/17 pass; stable over 3 reruns.
No app change — the scroll-restore logic was already correct.
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