One unavailable remote profile no longer holds the whole session sidebar
aggregate hostage until the 180s backend readiness deadline. Each remote's
session read now runs under its own bounded budget and settles allSettled-
style: healthy profiles' rows land immediately, the dead one contributes a
named error entry in the response payload instead of being swallowed to
null, and the underlying fetch keeps running so a slow-to-boot remote lands
on a later refresh. No sidebar visuals change — the renderer's existing
errors handling carries the failure.
Fixes#75712
049d2c2223