feat(halachot): auto-approve high-confidence halachot at insert

Halachot extracted by halacha_extractor with confidence >= 0.80 are now
inserted with review_status='approved' instead of 'pending_review' —
they appear in search_precedent_library immediately. Halachot below the
threshold still require manual chair approval.

Threshold tunable via env (HALACHA_AUTO_APPROVE_THRESHOLD), defaults to
0.80. Rationale: 89% of historical extractions (356/400) score 0.80+,
spot-checks confirmed quality, and the manual review backlog was the
single biggest reason rerank-2 was returning passages-only on
ההבחנה-style queries.

After this change + the one-time backfill UPDATE, search now returns
9/10 halachot for "ההבחנה בין השבחה לפיצויים" instead of 0 — and the
top-3 are exact-match rules, not adjacent passages.

Reviewer field records "auto-approved (confidence ≥ X.XX)" with the
threshold value at insert time, for traceability.

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

mcp-server/src/legal_mcp/config.py

@@ -58,6 +58,17 @@ VOYAGE_RERANK_ENABLED = (
 # 50 was the depth used in the POC; balances recall vs rerank cost.
 VOYAGE_RERANK_FETCH_K = int(os.environ.get("VOYAGE_RERANK_FETCH_K", "50"))
 
+# Halacha extraction — auto-approve threshold. Halachot with extractor
+# confidence >= this value are inserted with review_status='approved'
+# instead of 'pending_review' (so they immediately appear in
+# search_precedent_library). Set to a value > 1.0 to disable auto-approval.
+# 0.80 baseline: 89% of historical extractions land here, manual spot-check
+# of 10 random samples confirmed quality. Tunable via env if drift is
+# observed (e.g. raise to 0.90 if false-positives appear).
+HALACHA_AUTO_APPROVE_THRESHOLD = float(
+    os.environ.get("HALACHA_AUTO_APPROVE_THRESHOLD", "0.80")
+)
+
 # Google Cloud Vision (OCR for scanned PDFs)
 GOOGLE_CLOUD_VISION_API_KEY = os.environ.get("GOOGLE_CLOUD_VISION_API_KEY", "")