brain/gateway: prohibit mission_tasks.status as a write source (M4-3a phase 1) (#1479)

docs/native-kanban-sot/P0-MAP-CURRENCY-2026-08-29.md

@@ -73,12 +73,22 @@ SHARED-CONTRACT.md §5.1 phase 1 requires an N-1 patch that stops
 `mission_tasks.status` as a write source, plus a writer inventory, before any
 expand DDL.
 
-- **Sole status write path:** `packages/brain/src/mission-tasks.ts`
+- **Sole authoring write path:** `packages/brain/src/mission-tasks.ts`
   `create`/`update` (Drizzle insert/update on `mission_tasks`), invoked by
   `apps/gateway/src/missions/missions.controller.ts`. `update` accepts
   `Partial<NewMissionTask>`, so `status` is writable through both DTOs today.
   The same module also exposes `remove`/`removeByMission` DELETE paths —
   immaterial to `status` writes, listed for inventory completeness.
+- **Storage-layer surfaces that touch the column without authoring it**
+  (added 2026-08-29 after independent review of the phase-1 patch):
+  `packages/storage/src/migrate-tier.ts` copies whole `mission_tasks` rows
+  between storage tiers and must preserve the stored `status` verbatim — row
+  transport, exempt from the write prohibition (stripping there would corrupt
+  data inside the N-1 window). The generic table-keyed storage adapters
+  (`adapters/postgres.ts`, `adapters/pglite.ts`) register `mission_tasks` in
+  their table maps but have no caller that targets it: measured at this head,
+  every runtime adapter caller passes a fixed collection constant
+  (preferences/insights). Neither surface authors a new `status` value.
 - **Read-only consumers of `mission_tasks`:** federation verb services
   (`get-query.service.ts`, `list-query.service.ts`) select only. The MCP
   `brain_*` tools do not touch `mission_tasks` at all; `brain_create_task` /