[nimrod-teich]

#Closes MAG-4720

Jira ticket: MAG-4720

Summary

• The generated v1.6.5 Highlights said the router turns NotReady "when all of its relays fail". That is fix(readiness): turn NotReady when a router's relays all fail (MAG-4617) #581's rule. feat(readiness): readiness follows reachability, three-valued probe (MAG-4641) #586 (MAG-4641) replaced it before the release: a chain turns unhealthy only when no upstream answers, an error, an error status or a rate limit leaves it as it was, and only a result makes it healthy.
• feat(readiness): readiness follows reachability, three-valued probe (MAG-4641) #586 merged into fix(readiness): give each health-check try its own relay processor (MAG-4639) #584's branch and reached main inside fix(readiness): give each health-check try its own relay processor (MAG-4639) #584's squash commit (bb43ae9), so the generator listed no line for it.
• The Highlights now lead with the shipped rule: the three verdicts, the client relays and sibling interfaces that bring the check forward, and who notices. That covers a shared upstream outage keeping the Service populated, smartrouter_overall_health staying 1 through one, and the verdict field on the Health Check Interval Check log line.
• The wrong generated sentence is dropped. The rest of the generated paragraph follows, starting "Release v1.6.5 also refines…".
• Changes gets a hand-added feat(readiness) line for MAG-4641 pointing at bb43ae9, and a sub-bullet on each of the fix(readiness): turn NotReady when a router's relays all fail (MAG-4617) #581 and fix(readiness): give each health-check try its own relay processor (MAG-4639) #584 lines. The rest of the lists stay as the mechanical record.

Checks

• Every statement matches the code at the v1.6.5 tag:
  • recordProbeResult stores health only for ProbeHealthy and ProbeUnreachable;
  • probeOthersSoon exists;
  • the log line carries verdict and health result;
  • the defaults are 5 min and 15 s;
  • docs/METRICS.md has "When they change".
• scripts/extract-changelog.sh v1.6.5 returns the amended section, and every [#N] and commit reference in it has a link definition.

Release page

The v1.6.5 release body has been replaced with scripts/extract-changelog.sh v1.6.5 run on this branch, so it already reads as this PR does. Edits on the release page never sync back to CHANGELOG.md, so this file stays the source. If review changes the text, re-extract after merge.

Left unmerged for review.

Screenshots

No UI change.