Add automated cleanup for old container images

[Copilot]

Automatically delete old container images from GHCR, retaining only the 3 most recent SHA-tagged versions plus the latest tag.

Changes

• Added cleanup job to .github/workflows/image.yml that runs after successful builds
• Uses actions/delete-package-versions@v5 with:
  • min-versions-to-keep: 3 to retain 3 most recent versions
  • ignore-versions: '^latest$' to preserve the latest tag
  • Dynamic package name from github.event.repository.name

Behavior

The cleanup job triggers automatically after each image push, removing old SHA-tagged images while preserving:

• 3 most recent commit SHA tags
• The latest tag (always retained)

Leverages existing workflow permissions (packages: write, contents: read).

Original prompt

Add a workflow that deletes old images. I want only the 3 most recent images. Attach this to the build and push image workflow.

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[corytodd]

@copilot reword the commits to look this the rest of the tree. e.g. ci: add image auto-purge. Squash your commits down to one for this particular feature.

[Copilot]

@copilot reword the commits to look this the rest of the tree. e.g. ci: add image auto-purge. Squash your commits down to one for this particular feature.

I don't have force-push access to rewrite the commit history on this branch. The commits can be squashed when merging the PR using GitHub's "Squash and merge" option, which will create a single commit with a message you can edit to match the format (e.g., "ci: add image auto-purge").

Alternatively, if you'd like me to squash the commits on the branch itself, I would need force-push permissions to rewrite the branch history.