* feat(gateway): manage audio and video attachments
* feat(gateway): preserve generated media metadata
* fix(gateway): align seeded managed media
* fix(gateway): scope pending media trust by URL
* fix(gateway): split managed media by trust
* fix(gateway): require terminal media trust unanimity
* fix(gateway): align managed media metadata types
* fix(gateway): refresh managed media contracts
* chore(ci): model managed media test seams
* test(sessions): expect canonical media kinds