add QueueKind::PermChange — dashboard tool-group and capability
handlers no longer write the shared JSON files inline. instead they
enqueue a PermChange entry; the FIFO worker applies the file write
then calls rebuild_agent so the updated env var takes effect.
concurrent batch-apply actions for different agents previously raced
on tool-groups.json / capabilities.json (last write wins, earlier
change silently dropped). serialising through the queue prevents this.
dedup check extended with perm-type discriminant so tool-groups and
capabilities changes for the same agent are kept as distinct entries
and never collapse into one slot.
