feat(filters): panel removal + All-Books field-values fix (faceted plan Phase 8)

- Remove the Phase 7 facet-panel UI: SSR route, facet_panel.templ,
  FacetCountsForView, drawer panel block, panel TS + .facet-* CSS.
  The ENGINE stays (FacetCountsUnderFilters, all-facets endpoint,
  drift guard) — it becomes the Phase 9 builder's machinery.
- Fix the All-Books bug: field-values autocomplete (author/genre/
  tags/narrator/series/language) treats library_id as OPTIONAL —
  absent aggregates every VISIBLE library (family lens in-query);
  explicit out-of-set library_id is now 403, never a silent pass.
  The four scalar Search*Values queries get the nullable shape.
- toast.ts: suggestion fetches are exempt from error toasts
  (console-only) — a failed background hint never interrupts.
- TestFacetPanelPartial deleted with the behavior; TestFieldValuesAll-
  Libraries pins the fix (200 + cross-library aggregation, family
  lens, 403). Contract-pins changelog entry added.

web/static/input.css

@@ -874,41 +874,6 @@
     color: var(--text-secondary);
   }
 
-  /* ---------- Facet panel (filter drawer, Phase 7) ---------- */
-  /* The values are templ-rendered (templates/facet_panel.templ); this
-     is look only. A value button is plain until active: active means
-     "currently in that facet's filter" — accent-tinted like a chip. */
-  .facet-section-summary {
-    list-style: none;
-  }
-  .facet-section-summary::-webkit-details-marker {
-    display: none;
-  }
-  .facet-section-summary::before {
-    content: "▸";
-    display: inline-block;
-    margin-right: 0.5rem;
-    color: var(--text-secondary);
-    transition: transform 0.15s ease;
-    font-size: 0.7rem;
-  }
-  .facet-section[open] .facet-section-summary::before {
-    transform: rotate(90deg);
-  }
-  .facet-value-btn {
-    background-color: transparent;
-  }
-  .facet-value-btn:hover {
-    background-color: var(--surface-hover);
-  }
-  .facet-value-btn.facet-value-active {
-    background-color: var(--accent-muted);
-    color: var(--accent);
-  }
-  .facet-value-btn.facet-value-active span {
-    color: var(--accent);
-  }
-
   .loading-spinner {
     display: inline-block;
     width: 40px;