feat(corpus): Stage A — corpus tagging fixes + prevention layer

מתקן את הבאג של תיוג שגוי לועדות ערר ומונע חזרתו:

**Code changes:**
* New MCP tool `internal_decision_upload` (chair_name+district required)
  — sole supported path for ingesting committee decisions; tags
  source_kind='internal_committee' automatically.
* Citation guard in `precedent_library_upload` rejects citations starting
  with "ערר" or "בל\"מ" with a directive to use internal_decision_upload.
* `practice_area.py` taxonomy unification: PRACTICE_AREAS now accepts
  both multi-tenant (appeals_committee/national_insurance/labor_law)
  and domain (rishuy_uvniya/betterment_levy/compensation_197) values.
  New helper `to_db_practice_area(multi_tenant, subtype) -> domain`.

**Agent docs:**
* legal-researcher (+5K): upload-tool decision flowchart, code samples
  per source_kind, district enum (ירושלים/מרכז/תל אביב/צפון/דרום/חיפה/ארצי)
* legal-ceo, legal-analyst, legal-writer, legal-qa, HEARTBEAT — taxonomy
  awareness + source_kind-aware citation patterns + research_complete
  as valid status.
* Fixed two pre-existing wrong practice_area values in examples
  (histael_hashbacha→betterment_levy, pitsuim_197→compensation_197).

Closes TaskMaster #30(parts), #38(parts), #39 (root cause).
DB-side backfill + CHECK constraints applied directly via psql:
* 11 cases.practice_area corrected (1xxx→rishuy, 8xxx→betterment)
* 6 case_law records reclassified external_upload→internal_committee
  with inferred district
* 6 chair_name backfilled from full_text (5 שרית אריאלי + 1 דפנה תמיר)
* 88 new halachot extracted for newly-uploaded precedents
  (אנטרים + ירושלים שקופה 1112/22 + אגא וכט)
* CHECK constraints: cases.practice_area enum, case_law internal⇒district

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

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

@@ -63,6 +63,18 @@ async def precedent_library_upload(
     """
     if not citation.strip():
         return _err("citation חובה")
+    # Citation guard: appeals-committee decisions must go through
+    # internal_decision_upload (with chair_name + district). The legacy
+    # path always stored source_kind='external_upload' and left
+    # chair_name/district empty — see TaskMaster #30(ב).
+    _norm = citation.strip()
+    _committee_prefixes = ("ערר ", "ערר(", "ערר ", "בל\"מ ", "בל\"מ(", "ARAR ")
+    if any(_norm.startswith(p) for p in _committee_prefixes):
+        return _err(
+            "ציטוט שמתחיל ב-'ערר' או 'בל\"מ' הוא החלטת ועדת ערר. "
+            "השתמש ב-internal_decision_upload (דורש chair_name + district), "
+            "לא ב-precedent_library_upload."
+        )
     try:
         result = await precedent_library.ingest_precedent(
             file_path=file_path,