feat(ai-sdk): legal-corpus structure endpoint + coverage page

Expose GET /sdk/v1/rag/legal-corpus, which scrolls the eur-lex legal
corpus (filtered to a few hundred points regardless of total size) and
aggregates each ingested act's composition: distinct articles, annexes,
recitals and chunk count. Surface it as a new section on /sdk/coverage so
the ingested corpus is no longer a black box — a developer SEES what each
act actually contains, not only its name.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

admin-compliance/app/sdk/coverage/_helpers.ts

@@ -46,6 +46,28 @@ export interface CorpusOverview {
   totals: { documents: number; catalog_sources: number }
 }
 
+// --- Ingested legal-corpus structure (from the vector store, via the Go SDK).
+// Shows WHAT each eur-lex act consists of (articles/annexes/recitals), so the
+// ingested corpus is not a black box for developers. ---
+export interface LegalActStructure {
+  regulation_short: string
+  regulation_name: string
+  articles: number
+  annexes: number
+  recitals: number
+  chunks: number
+}
+
+export interface LegalCorpus {
+  regulations: LegalActStructure[]
+  totals: {
+    regulations: number
+    articles: number
+    annexes: number
+    recitals: number
+  }
+}
+
 // --- Korpus-Dokumente: gruppieren nach Art (Gesetz/Leitfaden/Standard/Urteil)
 // + Herausgeber-Familie (DSK, EDPB, OWASP, NIST …). Deterministisch, pure. ---
 interface DocCat {