feat(halacha-triage UI): wire gating + near-duplicate cluster cards (#84.2)

Completes #84 — surfaces the backend gating/prioritization (#84.1/#84.3, PR
#93) in the chair's review UI and adds near-duplicate clustering (#84.2).

Backend
- db.list_halachot gains `cluster` (#84.2): annotates each row with cluster_id +
  cluster_size by unioning same-precedent halachot within HALACHA_CLUSTER_COSINE
  (0.90, new config). Display-only — never merges/deletes. Pairwise is confined
  to the returned set (cheap).
- GET /api/halachot exposes the `cluster` query param (default off).

Frontend (web-ui)
- Halacha type gains optional cluster_id / cluster_size (hand-written module; no
  api:types regen needed — halachot aren't typed off the generated schema).
- useHalachotPending(opts): the default "clean" queue now fetches
  exclude_low_quality + order_by_priority + cluster; needsFix:true returns the
  flagged 'needs extraction fix' bucket (filtered client-side).
- HalachaReviewPanel: a "תור נקי / דורש תיקון-חילוץ" toggle (#84.1); near-dup
  clusters collapse into ONE card showing "+N וריאנטים" with an expandable list,
  and approve/reject/defer on a clustered card applies to all variants via the
  batch endpoint (#84.2 + #84.4). Counts show true halacha totals (pendingTotal).
  New flag labels added (application / near_duplicate / nevo_preamble_leak).

Verified:
- backend: list_halachot(cluster=True) on the live queue — algorithm correct
  (groups related same-precedent rules at 0.78; none at the production 0.90
  because dedup #82 already removed near-dups — the desired state).
- frontend: `tsc --noEmit` exits 0 (type-clean); no new lint errors (the one
  lint error is pre-existing in training/learning-panel.tsx from #94). Local
  Turbopack build can't run on the worktree node_modules symlink — CI builds in
  a clean checkout.

Invariants: G1 (gate/cluster at source in SQL, not post-hoc); G2 (same
list_halachot path); §6 (flagged items routed to a visible bucket, not dropped).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-ui/src/lib/api/precedent-library.ts

@@ -92,6 +92,11 @@ export type Halacha = {
    * negatively (distinguished/criticized/overruled). */
   corroboration_count?: number;
   corroboration_negative?: boolean;
+  /* #84.2 near-duplicate clustering (present only when fetched with cluster=true):
+   * same-precedent halachot within the cluster cosine share a cluster_id, so the
+   * UI collapses them into one review card. cluster_size === 1 → singleton. */
+  cluster_id?: string;
+  cluster_size?: number;
 };
 
 export type RelatedCase = {
@@ -566,14 +571,32 @@ export function useRequestHalachotExtraction() {
   });
 }
 
-export function useHalachotPending(limit = 200) {
+/** #84.1/#84.2/#84.3 — the chair review queue.
+ *
+ * Default ("clean") view: quality-gated (flagged items hidden), priority-ordered
+ * (most-uncertain/negatively-treated first), and near-duplicate-clustered into
+ * one card. Pass `needsFix: true` for the 'needs extraction fix' bucket — every
+ * pending item carrying a quality flag (filtered client-side). */
+export function useHalachotPending(
+  opts: { limit?: number; needsFix?: boolean } = {},
+) {
+  const { limit = 200, needsFix = false } = opts;
+  const qs = needsFix
+    ? `review_status=pending_review&exclude_low_quality=false&limit=${limit}`
+    : `review_status=pending_review&exclude_low_quality=true`
+      + `&order_by_priority=true&cluster=true&limit=${limit}`;
   return useQuery({
-    queryKey: libraryKeys.halachotPending(),
-    queryFn: ({ signal }) =>
-      apiRequest<{ items: Halacha[]; count: number }>(
-        `/api/halachot?review_status=pending_review&limit=${limit}`,
+    queryKey: [...libraryKeys.halachotPending(), needsFix ? "needsfix" : "clean"],
+    queryFn: async ({ signal }) => {
+      const res = await apiRequest<{ items: Halacha[]; count: number }>(
+        `/api/halachot?${qs}`,
         { signal },
-      ),
+      );
+      if (!needsFix) return res;
+      // needs-fix bucket = pending items that carry a quality flag
+      const items = res.items.filter((h) => (h.quality_flags?.length ?? 0) > 0);
+      return { items, count: items.length };
+    },
     staleTime: 5_000,
     refetchOnMount: "always",
   });