Point AGENTS.md at the one list of environment variable names

AGENTS.md

@@ -250,6 +250,19 @@ example logs an error that names the variable and the configurator.
   assets, and the IP Intelligence example tests use the Asn file and throw
   their output away.
 
+## Environment variable names
+
+[common-ci's list of environment variable names](https://github.com/51Degrees/common-ci/blob/d8a9c596eabf69dd5581a08e9360cdd1c9b3d9e8/environment-variables.md)
+holds every environment variable name that the packages, tests, examples and
+CI scripts of every language read, with what each name holds and the
+deprecated names each replaced. The list decides. Use the names it gives, and
+when a change needs a new name, or reads an old name again, change
+[`environment-variables.json`](https://github.com/51Degrees/common-ci/blob/d8a9c596eabf69dd5581a08e9360cdd1c9b3d9e8/environment-variables.json)
+in common-ci in the same piece of work. This repository's own name
+check, [`ci/check-environment-variable-names.ps1`](ci/check-environment-variable-names.ps1), still keeps a
+list of its own. Where the two differ, common-ci's list is the one to
+follow.
+
 ## Products keep their own CI scripts
 
 Each product folder still has the `ci/` scripts it had as its own repository,
@@ -321,14 +334,6 @@ draft and has no review requested. When a release is wanted, one pull request
 merges `rc` into `main`, and the "Only rc into main" check fails a pull request
 into `main` from any other branch.
 
-## Releases
-
-Pull requests go to `rc`, not `main`, and stay drafts until they have been
-reviewed, because the nightly merges any pull request into `rc` that is not a
-draft and has no review requested. When a release is wanted, one pull request
-merges `rc` into `main`, and the "Only rc into main" check fails a pull request
-into `main` from any other branch.
-
 ## History
 
 The four repositories were brought in with `git subtree add`, so commit SHAs