Function syncCommand

Sync a local directory to / from a B2 bucket prefix.

Direction is determined by the direction input (up = local → B2, down = B2 → local). With direction: auto (the default) we infer:

• if source is an existing local directory → up
• otherwise → down (source is a B2 prefix, destination is local)

The SDK's synchronize returns an AsyncGenerator<SyncEvent> which we relay to the workflow log (per-file) and aggregate into a typed result.