More precise Capability suggestions, browser sign-out and onboarding recovery

• Change-to-Capability suggestions distinguish domain migrations from database or schema migrations, recognizing references such as DB, Supabase, PostgreSQL, tables, and migration scripts.
• Single or bulk edits to existing record attributes stay with their existing Capability unless the source establishes a distinct workflow. Suggestions can recognize changes to an existing domain ability and a named interface separately when both are explicitly described.

Signing out clears the current browser session without invalidating active sessions for the same account in other browsers or devices.

• If Nova cannot start example preparation because the browser authentication session expired, the onboarding card says the session expired and offers Sign in again. That returns to /onboarding while keeping saved data.
• If Outcomet cannot send the example-preparation request before processing starts, Other options → Remove demo data is immediately available without a misleading removal error in the footer. It remains available on the website step so an existing demo package can be removed before switching to fallback demo data.