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/models.py

@@ -9,13 +9,18 @@ from uuid import UUID
 from pydantic import BaseModel, Field
 
 
-# Core case lifecycle — kept in sync with STATUS_ORDER in tools/cases.py and the
-# frontend SSoT web-ui/src/lib/api/case-status.ts. Trimmed from 17 → 10 (the
-# decorative mid-stage markers that no pipeline code ever set were removed).
+# Core case lifecycle. The canonical key set, order, labels, phases and (future)
+# per-status actions all live in ONE place — legal_mcp/case_status_model.py —
+# which asserts this enum matches it. The frontend mirror is
+# web-ui/src/lib/api/case-status.ts (generated against GET /api/status-model).
+# The analyst/research intermediate states are first-class canonical statuses
+# (the agents set them) — not legacy.
 class CaseStatus(str, enum.Enum):
     NEW = "new"
     PROCESSING = "processing"
     DOCUMENTS_READY = "documents_ready"
+    ANALYST_VERIFIED = "analyst_verified"
+    RESEARCH_COMPLETE = "research_complete"
     OUTCOME_SET = "outcome_set"
     DIRECTION_APPROVED = "direction_approved"
     QA_REVIEW = "qa_review"