feat(graph): in-app corpus citation graph (/graph) — Phase 1

Native, Obsidian-graph-view-like network of the precedent corpus, rendered
in web-ui from a read-only projection of the live DB. Replaces the idea of
exporting to an external Obsidian vault (which would be a parallel, drifting
copy of the corpus — the exact root cause G2 forbids).

The graph edges already existed in the data model; this only surfaces them:
nodes = precedents (case_law) + synthesized topic/practice-area hubs;
edges = cites (precedent_internal_citations) + same_chain (case_law_relations)
+ tagged/in_area (subject_tags / practice_area membership). Node size =
incoming-citation count (index-backed GROUP BY on idx_pic_target). Click a
node → local-graph neighborhood focus; panel deep-links to /precedents/[id].

Backend (read-only, SELECT only — G2):
- web/graph_api.py — Pydantic models (CorpusGraph/GraphNode/GraphEdge, so
  OpenAPI emits real types — UI2) + SQL assembly over the shared db.get_pool().
- web/app.py — GET /api/graph/corpus, GET /api/graph/node/{id}/neighborhood,
  both with explicit response_model. practice_area validated against the
  closed enum (G5); both endpoints write nothing.

Frontend:
- react-force-graph-2d (canvas/d3-force), loaded via next/dynamic ssr:false.
- /graph page + nav entry; graph.ts TanStack hooks; filter panel (practice_area
  / source / min-citations / search / node-type toggles), node detail panel,
  hover+selection neighborhood highlight. Explicit error handling (UI4).

Not a retrieval path (03-retrieval): returns graph topology, never ranked
search results. Halacha nodes + corroboration/equivalence edges are Phase 2,
already gated behind the node_types param (no contract change needed).

SQL validated read-only against the live DB (142 precedents, 85 resolved
citations, JSONB tag expansion, ANY(uuid[]) edge + BFS queries). web-ui lint
+ build pass; /graph in the route table.

Invariants: keeps G2 (single source of truth — live projection, no parallel
store), G5 (corpus separation filtered server-side), UI2 (response models),
UI4 (no swallowed UI errors).

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

web-ui/src/app/graph/page.tsx

@@ -0,0 +1,29 @@
+import Link from "next/link";
+
+import { AppShell } from "@/components/app-shell";
+import { GraphView } from "@/components/graph/graph-view";
+
+export default function GraphPage() {
+  return (
+    <AppShell>
+      <section className="space-y-6">
+        <header>
+          <nav className="text-[0.78rem] text-ink-muted mb-1">
+            <Link href="/" className="hover:text-gold-deep">
+              בית
+            </Link>
+            <span aria-hidden> · </span>
+            <span className="text-navy">מפת הקורפוס</span>
+          </nav>
+          <h1 className="text-navy mb-0">מפת הקורפוס</h1>
+          <p className="text-ink-muted text-sm mt-1 max-w-3xl">
+            רשת הציטוטים של ספריית הפסיקה — כל נקודה היא פסיקה או נושא, וקו מציין ציטוט או שיוך.
+            גודל הנקודה משקף כמה פעמים הפסיקה צוטטה. לחצו על נקודה כדי להתמקד בשכניה.
+          </p>
+        </header>
+        <div className="h-[2px] bg-gradient-to-l from-transparent via-gold to-transparent" />
+        <GraphView />
+      </section>
+    </AppShell>
+  );
+}