feat: Stage A finalizers + #35/#36/#37 — critical-gap closure

Four parallel sub-agents closed the remaining critical gaps from the
26/05 Stage A/B sprint. Each block independently tested; aggregated here.

## #30/#31 finalizers (sub-agent A)
* Auto-derive practice_area in case_create from case_number prefix
  (1xxx→rishuy_uvniya, 8xxx→betterment_levy, 9xxx→compensation_197);
  default for CaseCreateRequest is now "" (the DB constraint catches
  any stray "appeals_committee").
* practice_area.py: derive_subtype now handles axis-B domain values
  (rishuy_uvniya/betterment_levy/compensation_197) without parsing the
  case number; new helper derive_domain_practice_area().
* Halacha re-extraction verified unnecessary — all 6 reclassified
  records already had is_binding=false and approved halachot.
* Regression tests: 6 cases in tests/test_corpus_constraints.py
  covering practice_area enum, internal-committee chair/district,
  external-upload arar prefix, MCP guard.
* UI: district input → Select dropdown (7 districts) in
  precedent-edit-sheet.tsx, preserving legacy free-text values.

## #37 בל"מ subtypes (sub-agent B)
* 3 new appeal_subtypes: extension_request_{building_permit,
  betterment_levy,compensation}. APPEALS_COMMITTEE_SUBTYPES extended,
  SUBTYPES_BY_AREA mappings added.
* New helpers: is_blam_subject(), is_blam_subtype(),
  derive_subtype_with_blam(case_number, subject, practice_area).
  case_create now uses it to auto-detect "בקשה להארכת מועד" subjects.
* 3 methodology templates under docs/methodology/extension-request-*.md.
* paperclip_client.py mapping updated for the 3 new subtypes
  (extension_request_building_permit→CMP, the other two→CMPA).
* Frontend: bilingual "בל"מ" badge + filter dropdown on cases list +
  detail header; appeal-type-bars collapseBlam() merges בל"מ into its
  parent domain for aggregate bars.
* Wizard auto-detects בל"מ from subject during case creation.
* 3 Berlinger cases (1017/1018/1019-03-26) migrated to
  appeal_subtype=extension_request_building_permit via psql.

## #35 missing_precedents feature (sub-agent C)
* Schema V13: missing_precedents table (citation, case_id, party,
  legal_topic, status, linked_case_law_id, claim_quote, ...) +
  FK constraints + 3 indexes. Applied via psql + idempotent migration.
* 6 db.py service functions, 3 MCP tools, 6 FastAPI endpoints
  (POST/GET/PATCH/DELETE/upload — upload routes by citation prefix
  to ingest_internal_decision or ingest_precedent).
* Next.js page /missing-precedents with 5 status tabs + filters +
  sidebar badge counter + detail drawer with metadata edit + smart
  upload form that switches fields per committee/court.
* Bootstrap: 7 rows imported from the JSON file
  (3 citations × cases, all status=closed with linked_case_law_id).
* legal-researcher.md: new §2ב.5 with missing_precedent_create
  usage + dedup semantics + tool grant.

## #36 legal_arguments aggregation (sub-agent D)
* Schema V14: legal_arguments + legal_argument_propositions M:M.
  Applied via psql.
* New service argument_aggregator.py with two functions —
  aggregate_claims_to_arguments() (Claude CLI / claude_session) and
  get_legal_arguments(). Graceful llm_unavailable handling when CLI
  is missing (containers).
* 2 MCP tools + 2 API endpoints (POST .../aggregate-arguments as
  BackgroundTask, GET .../legal-arguments).
* Frontend: shadcn Accordion + new legal-arguments-panel.tsx with
  hierarchical (party → priority badge → arguments) display, "טיעונים"
  tab on the case page, "חשב/חשב מחדש" buttons.
* scripts/backfill_legal_arguments.py + SCRIPTS.md entry — dry-run
  found 8 candidate cases including 1017/1018/1019.

## Open follow-ups (intentionally deferred)
* npm run api:types in web-ui (CLAUDE.md flow) — recommended before
  the next UI commit; not required for backend deployment.
* Run backfill_legal_arguments.py --apply once the container picks up
  the new aggregator service.
* webhook on missing-precedents upload-close to Paperclip (optional).

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

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

@@ -0,0 +1,83 @@
+"""MCP tools — aggregated legal arguments (claim de-duplication)."""
+
+from __future__ import annotations
+
+import json
+from uuid import UUID
+
+from legal_mcp.services import argument_aggregator, db
+
+
+async def aggregate_claims_to_arguments(
+    case_number: str,
+    force: bool = False,
+) -> str:
+    """כינוס פרופוזיציות גולמיות לטיעונים משפטיים מובחנים.
+
+    Args:
+        case_number: מספר תיק הערר.
+        force: True = למחוק טיעונים קיימים ולחשב מחדש.
+    """
+    case = await db.get_case_by_number(case_number)
+    if not case:
+        return json.dumps(
+            {"status": "error", "message": f"תיק {case_number} לא נמצא."},
+            ensure_ascii=False, indent=2,
+        )
+
+    case_id = UUID(case["id"])
+    result = await argument_aggregator.aggregate_claims_to_arguments(
+        case_id, force=force,
+    )
+    result["case_number"] = case_number
+    return json.dumps(result, ensure_ascii=False, indent=2, default=str)
+
+
+async def get_legal_arguments(
+    case_number: str,
+    party: str = "",
+) -> str:
+    """שליפת טיעונים משפטיים מאוגדים לתיק.
+
+    Args:
+        case_number: מספר תיק הערר.
+        party: סינון לפי צד (appellant/respondent/committee/permit_applicant).
+               ריק = כל הצדדים.
+    """
+    case = await db.get_case_by_number(case_number)
+    if not case:
+        return json.dumps(
+            {"status": "error", "message": f"תיק {case_number} לא נמצא."},
+            ensure_ascii=False, indent=2,
+        )
+
+    case_id = UUID(case["id"])
+    args = await argument_aggregator.get_legal_arguments(case_id, party=party)
+
+    if not args:
+        return json.dumps({
+            "status": "empty",
+            "case_number": case_number,
+            "message": "לא נמצאו טיעונים מאוגדים. הרץ aggregate_claims_to_arguments תחילה.",
+            "arguments": [],
+        }, ensure_ascii=False, indent=2)
+
+    # Group by party for nicer display.
+    party_he = {
+        "appellant": "עוררים",
+        "respondent": "משיבים",
+        "committee": "ועדה מקומית",
+        "permit_applicant": "מבקשי היתר",
+        "unknown": "צד לא מזוהה",
+    }
+    by_party: dict[str, list[dict]] = {}
+    for a in args:
+        label = party_he.get(a["party"], a["party"])
+        by_party.setdefault(label, []).append(a)
+
+    return json.dumps({
+        "status": "ok",
+        "case_number": case_number,
+        "total": len(args),
+        "by_party": by_party,
+    }, ensure_ascii=False, indent=2, default=str)