Add .zip suffix to GHA artifacts

[rootnotez]

Motivation:
When looking at the artifacts for Build workflows it is not obvious to a user that they are .zip files. Adding .zip suffix would make this more clear.

Cause:
Internally the Build workflows use zip, but strip off the .ZIP suffix before uploading as artifact. See:
https://github.com/projectM-visualizer/projectm/actions/runs/20007036896/job/57370865288#step:10:18

Requires testing:
Are release flows expecting a non .ZIP suffix?

From my reading Release reads from Workflow name directly and does not read from Artifacts, and Release will use other compression tools as appropriate per platform (I.e. tar.gz). See https://github.com/ProjectM-visualizer/projectm/blob/master/.github/workflows/push_release.yml#L61-L63

[rootnotez]

Should I have squashed commits here? Sorry I did it in Github GUI.

[kblaschke]

GH Actions artifacts always use ZIP compression, you can't change it.

The release archives are always freshly packed on download, which is a completely different mechanism (it's actually the same link as the "code" button in the repo source view, just with a specific commit hash).

If you add an extension in the workflow, the downloaded file will be called <filename>.zip.zip because the extension is added automatically by GitHub (they may check if the artifact has an extension, but I guess they don't)

I've started the workflows, so you can try it out.

[kblaschke]

Here, that's what I mean.

[kblaschke]

I'll close this PR as there's really no way we can change this, and it doesn't make sense to add the extension twice.

The GitHub web UI shows the artifact name, without the extension, as it's used within actions. Artifacts will always be packaged into ZIP files as documented here, then hashed to ensure they've been uploaded or downloaded properly in workflows.

Code archives built from Git are a different feature, as these are compressed on-the-fly from the given Git commit, branch or tag. GitHub supports the .zip and .tar.gz extensions for the downloaded archive.

In a similar fashion, you can add the .patch or .diff suffixes to commit links to generate a unified diff or Git patch for that commit.