A group restore re-establishes a committed boundary this epoch did not run a
transition into, so its snapshot carries no decision and no controls for any
agent, and a fresh epoch is a new compositionDigest, so the descriptor takes the
next revision rather than republishing revision 1 with different contents.
CommittedSnapshot's rule becomes: null at boundary 0 and at an installed
boundary, always together, and for every agent or none -- a snapshot where one
fly acted and another did not would be two boundaries in one value. Dated
amendment to publishing-v1 section 3, with the schema set, the fixtures and the
TypeScript package moved together and the digest regenerated.