A review of the previous commit found that retrying at the plugin layer
(openStoredBotChat catching and re-calling host.openSession) didn't fix
the reported bug: host.openSession's own catch block unconditionally
calls setResumeExhaustedSessionId on a hydration timeout before
rethrowing, and only an explicit resumeSession() (the manual Retry
button) clears that latch for the currently-routed session. A
plugin-side retry is a different code path that can hydrate the
transcript fine while the full-screen "Couldn't load this session"
overlay stays latched over it.
host.openSession now takes a retryHydrationTimeoutOnce option and
retries the open+hydration-wait internally, before the latch is ever
set, so a successful retry never arms the overlay. openStoredBotChat
just opts in via that option.
6ec4aa8c3a