The "add collaborator" form currently fails if you submit a handle like @example.com, since the identity gets forwarded eventually directly to Bluesky's identity parse, which does not accept the @ prefix for handles.
This change is targetted to only fix that one form.
I do think it would be nice to put it in idresolver's ResolveIdent instead, but a change there seems like it could have wide effect across the app that i'm not equipped to test. Searching for strings.TrimPrefix shows manual stripping of @-prefixes in middleware, oauth, avatars, and keys, so I figure this direct change is consistent?
(I did not do a thorough survey of other handle handling that might also be missing @-stripping.)