feat(mcp): halacha_corroboration read-only tool (INV-COR6, X11)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/db.py

@@ -3439,6 +3439,28 @@ async def store_corroboration(
     )
 
 
+async def list_corroboration_for_halacha(halacha_id: UUID) -> list[dict]:
+    """Return all corroboration rows for one halacha, ordered by match_score DESC."""
+    pool = await get_pool()
+    rows = await pool.fetch(
+        "SELECT treatment, match_score, match_context, citing_case_law_id::text, "
+        "       citing_decision_id::text, created_at "
+        "FROM halacha_citation_corroboration WHERE halacha_id = $1 "
+        "ORDER BY match_score DESC", halacha_id,
+    )
+    return [
+        {
+            "treatment": r["treatment"],
+            "match_score": float(r["match_score"]) if r["match_score"] is not None else None,
+            "match_context": r["match_context"],
+            "citing_case_law_id": r["citing_case_law_id"],
+            "citing_decision_id": r["citing_decision_id"],
+            "created_at": r["created_at"].isoformat() if r["created_at"] else None,
+        }
+        for r in rows
+    ]
+
+
 async def search_precedent_library_semantic(
     query_embedding: list[float],
     practice_area: str = "",