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

test(capture): shoot the loading state, and stop racing the ones that are not master

Adds a popup-loading capture that holds two lookups open with Fetch interception, so the shot is of a popup on a slow network rather than a failed one, and documents it in status-states.md. Two changes to the harness it needed: --only re-shoots a single capture instead of rewriting fifteen real screenshots to say one thing, and every other scenario now waits for the card to drop aria-busy before the shot, since a capture taken mid-load is a capture of the placeholders.