Browser extension: detect and subscribe to standard.site publications on ATProto

feat(assets): share one popup-capture list between the store and the site master

scripts/shots.mjs names the popup captures shown to the public. The store listing screenshot composes from the entry marked store, and scripts/sync-shots.mjs copies the whole set into web/public/shots/ with a manifest of their real pixel sizes, so the two surfaces cannot advertise different builds of the popup. A prek hook re-syncs after a recapture.