The .feature spec lagged shipped behaviour. Added three files, no
duplication of existing scenarios:
- registration.feature: new Dex subject -> registration gate (users +
user_identities), returning subject straight through, account delete
is tapir-side only and leaves other users intact, clean
re-registration (ADR-012, ADR-013).
- summarize_mode.feature: auto summarizes every new video; manual
(default) leaves them unsummarized until queued; queued video is
processed and the flag cleared (migration 006).
- landing_page.feature: unauthenticated / -> /welcome, Get Started for
guests, summary link + logout for authed users, logout -> /welcome.
Scoped to built features only — no Vimeo/Whisper/billing scenarios.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
