test(api): every filter key the client sends is one the backend reads

FastAPI ignores an unknown query parameter, so a misspelt or renamed key silently stops a
filter while its chip still shows. Contract tests read routes/feed.py _feed_params and
plex/query.py LibraryFilters. The superseded feedCount/facets calls and keys are removed.

frontend/src/lib/api/feed.ts

@@ -151,10 +151,6 @@ function feedQuery(f: FeedFilters, cursor: string | null, limit: number): string
 export const feedApi = {
   feed: (f: FeedFilters, cursor: string | null, limit: number): Promise<FeedResponse> =>
     req(`/api/feed?${feedQuery(f, cursor, limit)}`),
-  // SUPERSEDED by feedSummary (PERF-13) — no component calls this anymore; the backend /feed/count
-  // endpoint it targets is kept only as the /feed/summary equivalence-test oracle. Retire together.
-  feedCount: (f: FeedFilters): Promise<{ count: number }> =>
-    req(`/api/feed/count?${filterParams(f).toString()}`),
   // Live YouTube search: results are materialised into the catalog and returned as feed cards.
   // `quiet` so the YT-search panel can render quota/limit errors (incl. 429) inline instead of
   // popping the global modal. `cursor` is the next-page token (an InnerTube continuation token
@@ -169,10 +165,6 @@ export const feedApi = {
   // the now-orphaned, un-kept videos). Returns how many videos were removed.
   clearSearch: (videoIds: string[]): Promise<{ removed: number }> =>
     req("/api/search/clear", { method: "POST", body: JSON.stringify({ video_ids: videoIds }) }),
-  // SUPERSEDED by feedSummary (PERF-13) — no component calls this anymore; the backend /facets
-  // endpoint it targets is kept only as the /feed/summary equivalence-test oracle. Retire together.
-  facets: (f: FeedFilters): Promise<{ counts: Record<string, number> }> =>
-    req(`/api/facets?${filterParams(f).toString()}`),
   // The sidebar's total count + per-tag channel facets in ONE request + ONE grouped query, replacing
   // the separate feedCount + facets the feed and sidebar used to fire on every filter change (PERF-13).
   feedSummary: (f: FeedFilters): Promise<{ count: number; facets: Record<string, number> }> =>