docs: fill in missing changelog entries

[billfreeman44]

Backfills and reconciles CHANGELOG.md for releases from the last ~30 days that shipped without changelog updates.

• Adds headings for released versions that had no entry.
• Where a heading's version number was ahead of the latest actual release (an anticipated bump that shipped under a different number), relabels it to the version it actually shipped in — no published version is renumbered.
• Only CHANGELOG.md is touched.

Part of a cross-repo changelog audit.