Trim the readme.txt changelog under wordpress.org's word limit

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- The `readme.txt` changelog lists 1.10.0 onward and links to this file for earlier versions. At 5,202 words it was over wordpress.org's 5,000-word limit, so the plugin page was silently cutting off the oldest entries.
+
 ### Fixed
 
 - After **Update citations**, the "Citation style changed" snackbar is dismissed, so it no longer sits beside the result still saying citations use the old style.

docs/release-readiness-checklist.md

@@ -96,6 +96,7 @@ miss — nothing in CI checks any of them.
 -   [ ] `package.json` and `package-lock.json` — not shipped, but keep in sync
 -   [ ] `CHANGELOG.md` has a section for this version
 -   [ ] `readme.txt` has both a Changelog entry and an Upgrade Notice
+-   [ ] `readme.txt`'s Changelog section stays under wordpress.org's 5,000-word limit (it truncates longer ones): keep the last ten or so versions and move the oldest out, leaving the "Earlier versions" link to `CHANGELOG.md`. Count with `awk '/^== Changelog ==/{f=1} /^== Upgrade Notice ==/{f=0} f' readme.txt | wc -w`
 
 ## Docs and fixtures