Mutation testing showed the negative structured-retries and expected-dim checks
in the env parsing path could be deleted with every test still passing. Their
value is the env key name in the message, so they need tests that assert it.
Changelog now states the real scope of this release and warns that normalising
scope moves the Redis keys, the one change here that silently relocates runtime
state. Records the breaker threshold derivation as deliberately env-only so it
does not resurface as another round.
iomgaa