Limit standalone issue references to 1-5 digits so 6-digit hex colours
like #222222 and #404141 are not parsed as GitHub issue numbers.
In --latest mode (used by the deploy pipeline), filter commits to only
those from the most recent commit's date so older commits without a tag
boundary cannot leak into a new release group via the issue fallback
cascade. This was causing 2026-04-10 release notes to incorrectly absorb
content from the 2026-04-06 #223 release.