Inbound sync was invisible to the machine it landed on — a local index,
cache or notifier had to poll. A `post_sync` command in the folder's own
.bdrive/config.json now runs once per cycle that applied peer changes,
with the batch as JSON on stdin.
The batch rides out on a new Result.Inbound rather than the inbound
spool: DrainInbound is destructive and `bdrive sync --hook` is its only
consumer, so a second drainer would silently empty the agent's
"teammates changed X" context. Both are kept, and both comments now say
why.
Cycle becomes a thin wrapper over cycleLocked so the hook is spawned
after the volume flock drops — a property of the code shape, not a rule
each of the seven call sites has to remember.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
