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/src/toast.ts

@@ -176,6 +176,18 @@ const setupHTMXListeners = (): void => {
   });
 };
 
+// Suggestion fetches — field-value autocomplete (author=, genre=, …)
+// on the search endpoint — are background hints for typed inputs. A
+// failed hint must never interrupt the user with a toast: it logs to
+// the console only. The grid's real search (q=/sort= params) is NOT a
+// suggestion fetch and keeps its toasts.
+const suggestionFieldRe = /[?&](author|genre|tags|narrator|series|language)=/;
+function isSuggestionFetch(input: Parameters<typeof fetch>[0]): boolean {
+  const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+  if (!url.includes("/api/media-items/search?")) return false;
+  return suggestionFieldRe.test(url) && !/[?&](q|sort)=/.test(url);
+}
+
 // Setup fetch interceptor
 const setupFetchInterceptor = (): void => {
   const originalFetch = window.fetch;
@@ -209,17 +221,28 @@ const setupFetchInterceptor = (): void => {
         return response;
       }
 
-      // Handle other errors
+      // Handle other errors. Suggestion fetches are exempt (console
+      // only) — a failed background hint never interrupts.
       if (!response.ok) {
         const errorMessage = await parseFetchError(response);
-        showToast(errorMessage, "error");
+        if (isSuggestionFetch(args[0])) {
+          console.warn(
+            `Suggestion fetch failed (${response.status}): ${errorMessage}`,
+          );
+        } else {
+          showToast(errorMessage, "error");
+        }
       }
 
       return response;
     } catch (error) {
       // Don't show toast for redirect errors
       if ((error as Error).message !== "Session expired") {
-        showToast("Network error: Unable to connect to server", "error");
+        if (isSuggestionFetch(args[0])) {
+          console.warn("Suggestion fetch failed: network error", error);
+        } else {
+          showToast("Network error: Unable to connect to server", "error");
+        }
       }
       throw error;
     }