Ports the core of Termix's host-transfer feature: stream files/directories
between two SSH hosts through the backend via SFTP (read source -> write dest),
with up-front scan for progress totals, recursive directory support, optional
move, and cooperative cancellation. Leaves behind Termix's parallel-segment
workers, tar heuristics, watchdogs and retry orchestration as unjustified at
this scale.
Exposed via REST (start/list/status/cancel) with an in-memory transfer registry,
and surfaced in the Files page as a per-entry "send to another host" action plus
a live transfers progress panel. Verified end-to-end against two real SSH
endpoints: recursive copy (binary md5 match), move (source deleted), error
handling, and mid-stream cancel.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BbJV5nm8KPVH1oNJYKpnoF
29c69224b2