The bus module sends snapshot-get's file in chunks and the recovery module
receives them; both now use buscalls.SeatChunks (subjects, body, receive),
so the form lives once in mesh-sdk.
Builds: design 47 G §681, A-64, A-139
Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h
