feat(proceeding-type): explicit ערר/בל"מ field for cases + corpus

Same case_number can exist as both a regular appeal (ערר) and an
extension-of-time request (בל"מ), and we were inferring the difference
from appeal_subtype prefixes — fragile, and case-number lookups
weren't disambiguated. Now stored as a first-class field on both
case_law (corpus) and cases (live cases), with partial unique indexes
on (case_number, proceeding_type).

- SCHEMA_V15: column + CHECK constraints + backfill from
  appeal_subtype LIKE 'extension_request_%' + partial unique indexes
  replace the old global UNIQUE(case_number).
- derive_proceeding_type() centralizes the inference rule
  (extension_request_* → בל"מ; subject regex fallback; default ערר).
- Metadata extractor prompt asks Claude to populate the new field
  explicitly; apply_to_record writes it for internal_committee rows.
- internal_decision_upload, case_create, case_update accept an
  optional proceeding_type; FastAPI request models expose it.
- Wizard + edit dialog get a sided Select; case header renders the
  resolved label (ערר / בל"מ).
- Uploaded the 2 staged בל"מ decisions on betterment levy:
  8126/24 (סופר נוח, 13 chunks), 8047/23 (הרנון, 48 chunks).

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

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

@@ -130,6 +130,7 @@ async def case_create(
     expected_outcome: str = "",
     practice_area: str = "",
     appeal_subtype: str = "",
+    proceeding_type: str = "",
 ) -> str:
     """יצירת תיק ערר חדש.
 
@@ -150,6 +151,7 @@ async def case_create(
                         אוטומטית ממספר התיק (1xxx→רישוי, 8xxx→השבחה, 9xxx→197)
         appeal_subtype: סוג ערר (building_permit / betterment_levy / compensation_197).
                         ריק = יוסק אוטומטית ממספר התיק
+        proceeding_type: 'ערר' / 'בל"מ'. ריק = יוסק מ-appeal_subtype/subject.
     """
     from datetime import date as date_type
 
@@ -173,6 +175,11 @@ async def case_create(
         appeal_subtype = derived_subtype
     pa.validate(practice_area, appeal_subtype)
 
+    # proceeding_type: explicit override > derived from subtype/subject > 'ערר'
+    resolved_proc = proceeding_type.strip() or pa.derive_proceeding_type(
+        appeal_subtype=appeal_subtype, subject=subject,
+    )
+
     case = await db.create_case(
         case_number=case_number,
         title=title,
@@ -187,6 +194,7 @@ async def case_create(
         expected_outcome=expected_outcome,
         practice_area=practice_area,
         appeal_subtype=appeal_subtype,
+        proceeding_type=resolved_proc,
     )
 
     # If the user overrode the case-number convention (e.g. case 8500 marked
@@ -290,6 +298,7 @@ async def case_update(
     respondents: list[str] | None = None,
     property_address: str = "",
     permit_number: str = "",
+    proceeding_type: str = "",
 ) -> str:
     """עדכון פרטי תיק.
 
@@ -307,6 +316,7 @@ async def case_update(
         respondents: רשימת משיבים חדשה
         property_address: כתובת נכס חדשה
         permit_number: מספר תכנית/בקשה חדש
+        proceeding_type: 'ערר' / 'בל"מ' — ריק = ללא שינוי
     """
     from datetime import date as date_type
 
@@ -359,6 +369,12 @@ async def case_update(
         fields["property_address"] = property_address
     if permit_number:
         fields["permit_number"] = permit_number
+    if proceeding_type:
+        if proceeding_type not in {"ערר", 'בל"מ'}:
+            raise ValueError(
+                f"proceeding_type לא תקין: {proceeding_type!r}. ערכים תקפים: ערר / בל\"מ"
+            )
+        fields["proceeding_type"] = proceeding_type
 
     updated = await db.update_case(UUID(case["id"]), **fields)