feat(filter): label endpoint names id values for client-held trees

The SSR embed (65f257f3) covers trees the server renders; one path
still fell through to the flawed fallback — applying a SAVED filter
from a cold bookshelf. That page was rendered before any filter
existed (nothing embedded), and the fallback reused the suggest facet,
whose rows are MEDIA-CONSTRAINED: "feed in [A,B,C] AND title contains
Chapter" labeled only the feeds with a matching episode (the exact
live repro from the original bug report).

- GET /api/filter/labels?field=X&ids=a,b,c resolves names straight
  from the entity tables via the shared ResolveFieldLabels core
  (extracted from FilterTreeLabels): no media join, no tree
  constraint. RLS/visibility ride the request identity — a
  zero-episode subscribed feed resolves its title (pinned; the facet
  path structurally could not), an unsubscribed feed id stays unnamed
  (pinned), non-id fields are 400 (pinned), ids cap at 100.
- Client: resolveIdLabels/resolveLabelsAsync use ONLY the endpoint;
  the quiet suggest-fetch mode is deleted (its only caller was the
  flawed fallback). The saved-filter apply flow resolves through the
  endpoint and rebuilds the chips bar when labels land — chips render
  raw ids only while the round trip is in flight, never stuck.
- 188 web tests green; Go endpoint pins + filter/episode slices green;
  contract_pins documents the endpoint and the fallback removal.

web/src/bookshelf.ts

@@ -287,6 +287,15 @@ Alpine.data("bookshelf", () => ({
       // Rehydrate the rule-builder tree from the refilled form
       builderData()?.hydrateFromForm();
 
+      // Cold-cache labels (2026-11-01): this page was rendered BEFORE
+      // the filter existed, so the SSR embed has no names for the saved
+      // filter's ids — resolve through the label endpoint, then rebuild
+      // the chips (without the refresh they'd show raw ids until the
+      // next grid event).
+      void builderData()
+        ?.resolveLabelsAsync()
+        .then(() => refreshFilterChips());
+
       // Trigger HTMX to apply the filter by submitting the form
       window.htmx.trigger(filterForm, "submit");