Complete v19 Studio media administration

[lowestprime]

Summary

• Add the no-navigation Studio autosave mutation shell and preserve exact piece selection, viewport, focus, and canonical route state.
• Add explicit media-folder rule preview/apply workflows with reviewed direct-public assignment and protected-media publication gates.
• Synchronize normalized piece/media relations with legacy compatibility fields transactionally, including batch rollback and shared-media ownership handling.
• Add focused migration, media access, folder-rule, transaction, and source-contract regression coverage.

Why

The v19 Studio completion work needs durable, non-disruptive editing and a safe way to classify media without silently publishing protected assets or allowing legacy compatibility fields to overwrite normalized assignment truth.

Files / areas touched

• Studio piece and media editors, media picker, and Studio route state.
• Media actions, access policy, folder-rule engine, normalized piece-media persistence, and schema migration 8.
• Database migration, media transaction, media access, folder-rule, and piece-media tests.

Validation

• npm run test - passed, 125/125 tests.
• Focused WP03 media/migration suite - passed, 27/27 tests.
• npm run typecheck - passed.
• npm run lint - passed with 0 errors and 9 existing no-img-element warnings.
• npm run build - passed with safe standalone artifact checks.
• Disposable schema 0/6/8 migration and restart-idempotency matrix - passed.
• Fresh authenticated Chromium acceptance at desktop/mobile and light/dark - passed, including direct assignment, visibility transitions, protected-media denial, rollback, stale conflict, and canonical hard reload.

Caveats / follow-up

• This pull request remains draft while WP05-WP08, production-clone validation, backup/restore, deployment, rollback, and Tier 3 live evidence are pending.
• Browser acceptance used a disposable SQLite database and synthetic media only; no production data or media was mounted or mutated.
• Local persistence uses node:sqlite, and current build logs show Node's experimental warning for that API; public deployment should move to Postgres, LibSQL, or another stable production database.