One overload abort preserves the transcript so a retry can still win (#115906).
But when every summary attempt keeps aborting under a sustained outage the
transcript only grows until the session exits compression_exhausted, which the
gateway answers with an auto-reset discarding the ENTIRE transcript — bounded
middle-window loss becomes total session loss, deferred.
After 3 consecutive overload aborts in one session the overload stops counting
as a terminal summary failure and compress() commits the deterministic fallback
(failure_class=summary_overload_degraded) — the same bounded degrade the
repeated-stall ladder already takes (#112420). A successful summary resets the
budget; abort_on_summary_failure=true still hard-aborts every attempt.
Fixes#123167
(cherry picked from commit 2941aadffa71a3623aee26dfb1109106b0555741)
a5e8ad9f02