feat(status): single source of truth for the case-status model + canonicalize intermediates

Fixes the case where the H1 chip, the pipeline stepper and the manual-changer
dropdown disagreed (e.g. 1043-02-26 on analyst_verified): the status sat between
the canonical 10 and a legacy bucket, so each surface read a different list.

Root fix — ONE authoritative status model + canonicalize the real intermediate
states (chair-approved):

- New mcp-server/.../case_status_model.py — the single registry: ordered
  StatusDef list (key/label/description/phase/selectable/terminal/on_enter),
  the 5 phases, STATUS_ORDER, phase_of/label_of, and a drift assertion that the
  CaseStatus enum matches it. `on_enter` is the seam for a status to *do*
  something on entry, declared next to its definition (no dispatcher wired yet).
- models.CaseStatus enum: analyst_verified + research_complete promoted to
  first-class canonical statuses (the agents set them — they belong in the
  model, not a legacy fallback).
- tools/cases.py: the forward-only STATUS_ORDER guard now derives from the
  registry instead of an inline list.
- GET /api/status-model exposes the model so the frontend mirror can be
  generated against it.
- web-ui case-status.ts mirrors it: the two intermediates moved from the
  legacy map into CASE_STATUSES / PHASES(thinking) / STATUS_LABELS /
  STATUS_DESCRIPTIONS; status-badge icons+tones extended. So the chip (status),
  stepper (its phase) and dropdown (now includes it) all agree.

Invariants: G2 — collapses the scattered status definitions (enum, inline
STATUS_ORDER, two frontend label maps) onto one backend authority + a documented
frontend mirror; no parallel status list remains. Agent-prompt alignment +
backfill follow in a separate change. py_compile + tsc + eslint clean.

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

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

@@ -13,6 +13,7 @@ from uuid import UUID
 import httpx
 
 from legal_mcp import config
+from legal_mcp.case_status_model import STATUS_ORDER  # status SSoT
 from legal_mcp.services import audit, db, extractor, git_sync, practice_area as pa
 from legal_mcp.tools.envelope import empty, err, ok  # GAP-48: SSoT envelope
 
@@ -341,16 +342,8 @@ async def case_update(
     """
     from datetime import date as date_type
 
-    # Ordered core lifecycle — regression protection (forward-only).
-    # Single source of truth, mirrored by web-ui/src/lib/api/case-status.ts and
-    # models.CaseStatus. Trimmed from 17 → 10 (decorative statuses removed).
-    STATUS_ORDER = [
-        "new", "processing", "documents_ready",
-        "outcome_set", "direction_approved",
-        "qa_review", "drafted",
-        "exported", "reviewed", "final",
-    ]
-
+    # Ordered core lifecycle (forward-only regression guard). Single source of
+    # truth: legal_mcp/case_status_model.py — STATUS_ORDER/BY_KEY derive from it.
     case = await db.get_case_by_number(case_number)
     if not case:
         return err(f"תיק {case_number} לא נמצא.")
@@ -363,6 +356,9 @@ async def case_update(
         # Only update if advancing or status is unknown to the order
         if new_idx >= cur_idx or new_idx == -1:
             fields["status"] = status
+            # per-status on_enter hook (case_status_model) — the single place a
+            # status's behaviour is declared. No dispatcher wired yet; when the
+            # first action is added, dispatch BY_KEY[status].on_enter here.
     if title:
         fields["title"] = title
     if subject: