Decision 2026-04-18: container-level packet concerns (atomic
.tmp/rename, multi-pkt rotation, BSO .flo/.bsy, ArcMail bundles,
packet-header construction) belong in a new sibling library
fpc-ftn-transport, not in fpc-msgbase. ma.fmt.pkt(.uni) stays
here as the per-message reader/iterator surface.
This commit updates the PKT entry in docs/API.md's format
cheat-sheet so consumers reading it today know where the write-
side container API will live, instead of expecting it under
fpc-msgbase eventually. fpc-ftn-transport itself doesn't exist
yet -- this is a scope-boundary signal.
Driven by NetReader / Fimail consumer-round-1 feedback: the
storage-vs-transport split that already separates fpc-msgbase
from comet generalizes well; PKT is 70% transport with a
message-iteration angle, and the angle is the only reason it
fit here at all.
No code change.
Ken Johnson
4a3da2a6f6