Follow-up to PR #94531 salvage:
- classify the auxiliary boundary's terminal 'None response' /
'invalid response' errors (#7264) into the same empty-content abort
carve-out so those shapes also preserve the session (#94459's wider
classification, sibling shapes from #94448)
- register _last_summary_empty_content_failure in
_COMPRESSOR_ATTEMPT_STATE_FIELDS so pre-commit hard-cancel rollback
restores the flag (conversation_compression snapshot allow-list)
- tests: cooldown re-entry keeps aborting; both sibling shapes abort
- attribution: map zhangyswx@163.com -> YusenZhang0601
4ba2608524