Standby-redirect half is done and correct: OP_upgradeConfig has no
server-side redirect wiring today, matches design.md's own documented
"Out of Boundary" gap, and this test locks in the real current
rejection behavior.
Primary-push success-path half is unreliable (~24/25 live fails in one
investigation round, see bug-1485) -- the elected primary was observed
as a <defunct> zombie shortly after promotion, but a dedicated debug
pass could not reproduce it in 26+ clean runs on an idle host and
captured no crash evidence either way. tasks.md marks 6.3 _Blocked:_
pending re-verification on an idle host with real stderr capture.