[squarepots]

Changes

The nightly installer still derives its default image tag from the first version value in the nightly manifest. Current manifests put the stable coolify.v4.version first, while regular next builds publish the rolling next tag plus traceable immutable tags; exact RC tags are created only by the reviewed RC release workflow.

This changes the default nightly installer target to next and keeps explicit version arguments as overrides. It removes the identical nightly manifest, uses root versions.json for both CDN destinations, and updates the release guide to edit the intended RC base once.

Stable installer parsing, regular next builds, and exact RC publication semantics remain unchanged. Persistent runtime channel selection through VERSIONS_URL, UPGRADE_SCRIPT_URL, CheckForUpdatesJob, and UpdateCoolify is tracked separately in #11925.

Issues

• Fixes Nightly installer resolves the stable Coolify image #11909
• Nightly instances lose the rolling update channel after installation #11925 is the separate runtime-channel follow-up.

Category

• Bug fix
• Improvement
• New feature
• Adding new one click service
• Fixing or updating existing one click service

Preview

Not applicable: no UI change is included.

AI Assistance

• AI was NOT used to create this PR
• AI was used (please describe below)

Tools used: Codex.
How extensively: Used to update this PR description only; the implementation and validation statements are preserved from the existing PR.

Testing

Regression coverage checks the nightly default and override structure, stable installer behavior, root manifest ownership, CDN mapping, and existing next/RC workflow semantics. Shell syntax checks pass for both installer and upgrade-script pairs. No local Coolify development-instance test was performed as part of this metadata-only update.

Contributor Agreement

Important

• I have read and understood the contributor guidelines. If I have failed to follow any guideline, I understand that this PR may be closed without review.
• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate.
• I have tested all the changes thoroughly with a local development instance of Coolify and I am confident that they will work as expected when a maintainer tests them.

[Cinzya]

@squarepots it is important to us, that you do actually run manually tests locally on your changes. Also make sure to actually read our contributor guidelines.