Update copilot-instructions with versioning guidelines (#1177)

Author: gionn

.github/copilot-instructions.md

@@ -17,6 +17,11 @@ This repository contains shared/reusable CI configurations for GitHub Actions se
 echo "v9.1.0" > version.txt
 ```
 
+When referencing internal actions in workflow YAML files, **always use the latest released tag** (e.g., `v9.2.0`).
+Do **not** update these references to the next release version (e.g., `v9.3.0`) **in a pull request that is bumping the version** in `version.txt`.
+This is because the new tag (e.g., `v9.3.0`) will only be created and pushed at the end of the release build process.
+If you update the reference before the tag exists, the master build will fail after merging, as the referenced tag does not yet exist.
+
 ### Documentation Requirements
 
 **Always update `docs/README.md`** when adding or modifying GitHub Actions:
@@ -136,6 +141,7 @@ pre-commit run --all-files
 
 - Releases are triggered automatically when PRs are merged to master
 - The version in `version.txt` determines the release tag
+- Actions will automatically be updated with the release tag by the release workflow itself, no need to do it manually
 - Release notes are auto-generated from PR titles and descriptions
 - The `release.sh` script automatically updates all internal version references that use version tags
 - **CRITICAL**: Internal references must use version tags (not SHA pins) for automatic updates to work