Development record

The v0.15.1 release review found at commands/peers.md:78-80: STALE. The page says `released_by` is '`tombstone`, or `default-branch` when the record is already resolved...'. The code also emits `tag` (internal/core/claim/release.go:46, ReleasedByTag) for a release reservation whose tag vX.Y.Z is on origin, and commands/reserve.md documents it as '`released_by: tag`'. Fix: add `tag` (a release whose tag is on origin) to the list.