feat(search): add header global search (Phase A) — cases + precedents + docs

Adds an always-visible debounced search input in the AppShell header
that fans out to three independent sources in parallel and renders
per-source result groups with their own loading/empty/error states:

- /api/search/cases (NEW): SQL ILIKE on case_number, address, parties,
  title, subject. Returns small projections, no embeddings needed.
- /api/precedent-library/search (existing): semantic over case-law
  halachot + passages.
- /api/search (existing): semantic over case documents + past decisions.

Cmd/Ctrl+K focuses the input; Esc and click-outside close the panel.
This is Phase A of the header redesign — the bar layout itself is
unchanged; row grouping + dynamic context follow in Phase B.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web-ui/src/lib/api/global-search.ts

@@ -0,0 +1,113 @@
+/**
+ * Global header search — fans out to three independent sources in parallel.
+ *
+ * Each source is its own `useQuery`, so the fastest one (cases, plain SQL)
+ * shows up immediately while the slower vector searches stream in. A failure
+ * in one source does not block the others — the result panel renders per-
+ * source skeletons and per-source error states.
+ *
+ * Sources:
+ *   - cases     → GET /api/search/cases (SQL ILIKE on case_number/address/parties)
+ *   - precedent → GET /api/precedent-library/search (semantic, halachot+chunks)
+ *   - documents → GET /api/search (semantic, all case docs + past decisions)
+ */
+
+import { useQuery } from "@tanstack/react-query";
+import { apiRequest } from "./client";
+import type { SearchHit as PrecedentHit } from "./precedent-library";
+
+export type CaseHit = {
+  case_number: string;
+  title: string;
+  property_address: string | null;
+  status: string | null;
+  practice_area: string | null;
+  appeal_subtype: string | null;
+};
+
+export type DocumentHit = {
+  score: number;
+  case_number: string;
+  document: string;
+  section: string;
+  page: number | null;
+  content: string;
+};
+
+const MIN_QUERY_LEN = 2;
+const STALE_MS = 10_000;
+const PER_SOURCE_LIMIT = 5;
+
+const enabled = (q: string) => q.trim().length >= MIN_QUERY_LEN;
+
+export function useCasesSearch(query: string) {
+  return useQuery({
+    queryKey: ["global-search", "cases", query],
+    queryFn: ({ signal }) =>
+      apiRequest<{ items: CaseHit[]; count: number }>(
+        `/api/search/cases?q=${encodeURIComponent(query)}&limit=${PER_SOURCE_LIMIT}`,
+        { signal },
+      ),
+    enabled: enabled(query),
+    staleTime: STALE_MS,
+    placeholderData: (prev) => prev,
+  });
+}
+
+export function usePrecedentSearch(query: string) {
+  return useQuery({
+    queryKey: ["global-search", "precedent", query],
+    queryFn: ({ signal }) => {
+      const p = new URLSearchParams({
+        q: query,
+        limit: String(PER_SOURCE_LIMIT),
+        include_halachot: "true",
+      });
+      return apiRequest<{ items: PrecedentHit[]; count: number }>(
+        `/api/precedent-library/search?${p.toString()}`,
+        { signal },
+      );
+    },
+    enabled: enabled(query),
+    staleTime: STALE_MS,
+    placeholderData: (prev) => prev,
+  });
+}
+
+/**
+ * The /api/search endpoint returns either an array of DocumentHit, or
+ * `{message: "לא נמצאו תוצאות."}` when empty. Normalize to a plain array.
+ */
+export function useDocumentsSearch(query: string) {
+  return useQuery({
+    queryKey: ["global-search", "documents", query],
+    queryFn: async ({ signal }) => {
+      const raw = await apiRequest<DocumentHit[] | { message: string }>(
+        `/api/search?query=${encodeURIComponent(query)}&limit=${PER_SOURCE_LIMIT}`,
+        { signal },
+      );
+      return Array.isArray(raw) ? raw : [];
+    },
+    enabled: enabled(query),
+    staleTime: STALE_MS,
+    placeholderData: (prev) => prev,
+  });
+}
+
+export function useGlobalSearch(query: string) {
+  const cases = useCasesSearch(query);
+  const precedent = usePrecedentSearch(query);
+  const documents = useDocumentsSearch(query);
+
+  const isQueryReady = enabled(query);
+  const anyLoading =
+    isQueryReady && (cases.isLoading || precedent.isLoading || documents.isLoading);
+
+  return {
+    cases,
+    precedent,
+    documents,
+    isQueryReady,
+    anyLoading,
+  };
+}