refactor: remove retired data format support

docs/DEPLOYMENT.md

@@ -111,7 +111,10 @@ The workflow:
 7. waits for `/api/health/database` to report healthy;
 8. retains the logs and exits unsuccessfully if health verification fails.
 
-The outage covers backup, migration, and container startup.
+The outage covers backup, migration, and container startup. Migrations may also
+remove records that use retired data formats when a release explicitly ends
+compatibility. The deployment backup remains the recovery source for those
+records; the application does not repair or reinterpret them at runtime.
 The scheduler calls a bearer-authenticated endpoint on the application service
 once per minute. Scheduled message delivery therefore uses the web process's
 existing embedded-database connection instead of opening the locked database
@@ -123,7 +126,9 @@ consolidation, and email digest checks and is not published through a host port.
 Initialize the first staging release from the development database, including
 users, roles, builds, guides, proposals, audit history, avatars, and uploaded
 game-data icons. The staging importer refuses a target database that contains
-users, builds, audits, or proposals.
+users, builds, audits, or proposals. It also requires the source and target
+table sets to match exactly; snapshots with retired or unknown tables are
+rejected.
 
 First stop this project's development server. The embedded database must not be
 open while its complete transfer bundle is created: