fix(retrieval): restore _base(limit=) contract in hybrid precedent search

`rerank.maybe_rerank` calls `base_search(limit=…, **base_kwargs)` on both
the rerank-on and rerank-off paths. Commit 242f668 moved the closure into
hybrid_search.py and renamed its parameter to `limit_inner`, so every call
to `/api/precedent-library/search` raised TypeError 500 regardless of the
VOYAGE_RERANK_ENABLED flag. Sibling `search_documents_hybrid` was unaffected
because it uses `lambda **kw:` which absorbs the kwarg.

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

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

@@ -92,7 +92,7 @@ async def search_precedent_library_hybrid(
     """Hybrid wrapper for precedent-library search."""
     fetch_k = max(limit, config.VOYAGE_RERANK_FETCH_K) if config.MULTIMODAL_ENABLED else limit
 
-    async def _base(limit_inner: int) -> list[dict]:
+    async def _base(limit: int) -> list[dict]:
         return await db.search_precedent_library_semantic(
             query_embedding=query_text_embedding,
             practice_area=practice_area,
@@ -101,7 +101,7 @@ async def search_precedent_library_hybrid(
             appeal_subtype=appeal_subtype,
             is_binding=is_binding,
             subject_tag=subject_tag,
-            limit=limit_inner,
+            limit=limit,
             include_halachot=include_halachot,
         )