feat(halacha): lighter effort for BULK queue-drain extraction (speed at scale)

xhigh is the quality sweet-spot for a single precedent but very slow at scale
(64-chunk case ≈ 20 min). Bulk queue-drains (process_pending over many
precedents) now use a lighter effort to cut wall-clock; interactive single
re-extraction keeps xhigh quality.

- config.HALACHA_BULK_EXTRACT_EFFORT (env, default 'high'; set 'medium' for max
  speed, 'xhigh' to match single).
- extract()/_extract_impl()/_extract_chunk() take an `effort` override threaded
  to claude_session.query_json; None falls back to HALACHA_EXTRACT_EFFORT (xhigh).
- process_pending_extractions(kind='halacha') passes the bulk effort; single
  reextract_halachot keeps xhigh.

Verified end-to-end (mocked LLM): _extract_chunk(effort='medium') → query_json
effort='medium'; effort=None → 'xhigh' fallback. Closes the open item in #72.

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

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

@@ -219,7 +219,12 @@ async def process_pending_extractions(kind: str = "metadata", limit: int = 20) -
     async def _run_once(cid: UUID) -> dict:
         if kind == "metadata":
             return await precedent_metadata_extractor.extract_and_apply(cid)
-        return await halacha_extractor.extract(cid)
+        # Bulk queue-drain → lighter effort (config.HALACHA_BULK_EXTRACT_EFFORT,
+        # default 'high') to cut wall-clock at scale. Resume (force=False) so an
+        # interrupted drain continues per-chunk. Single re-extract stays xhigh.
+        return await halacha_extractor.extract(
+            cid, effort=config.HALACHA_BULK_EXTRACT_EFFORT,
+        )
 
     results: list[dict] = []
     processed = 0