v1 notifications, and those a stream tells, carried an 'ungrouped' key, so
a client reading grouped notifications could not fold a new like into the
group of likes it already shows. Each now names the group it belongs to by
default (likes and boosts of one post, follows within an hour).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw