Read results now flag content owned by someone else as 'foreign'

What

• db_read results now include a foreign: true field when the document was authored by someone else, the collection is access-controlled, or the caller isn't the document's owner.
• The artifact tool's read_asset action similarly flags results as foreign: true when the asset's page is a workshop page or otherwise not the caller's own; delete_asset now also returns a written: { url } object on successful deletion.
• The artifact tool's verify, list_files, and read_file actions now add foreign: true when the artifact or file belongs to another workshop/session (detected via workshop-page recording or, for read_file, a workshop-decisions marker in the HTML).
• New schemas back this: a written object (url) and a verify object (url, ver, state, entries, truncated, dropped, waited, and the new optional foreign flag).

Why Surfacing ownership this way helps Claude Code (and anyone reviewing its actions) tell apart content it owns from content that belongs to someone else's workshop or session, which matters for deciding whether it's safe to edit or delete.