A full-history load of a remote SSH session reads the scrollback from the
remote tmux in one bounded ssh round trip and splices it above the local
frame. A transport failure (ssh 255, timeout, unparseable output) starts a
30 s per-host back-off; a missing remote session is per-session only.
Conflict resolved in session-routes.ts: #602's remote scrollback read runs
before #601's capture helper and its alternate-screen fallback.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>