Simplify Docker tag publishing workflow

[lovasoa]

Summary

• Replace the generated Docker matrix plus exclude rules with explicit platform/variant entries carrying their tag suffix.
• Remove the shell step that recomputed those suffixes from the platform name.
• Remove Docker metadata JSON parsing from the final manifest job; the manifest tags are now spelled directly from the Git ref and variant suffix.

Complexity diagnosis

• The same tag suffix concept was previously derived in several places: matrix exclusions, a shell step, cache names, artifact names, and final manifest tags.
• The Docker matrix generated impossible or special-case combinations and then excluded them, which made the actual published images harder to see.
• The final manifest step used docker/metadata-action output only to parse it back into CLI flags, obscuring that it publishes just the current branch/tag and latest on release tags.

Validation

• git diff --check -- .github/workflows/ci.yml
• actionlint .github/workflows/ci.yml

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Sanitize the ref before using it as a Docker tag

When a valid release tag matching the workflow's v* filter contains Docker-invalid characters, such as the valid SemVer tag v1.2.3+build.1, this constructs an invalid image reference and docker buildx imagetools create fails, preventing the version and latest manifests from being published. The removed docker/metadata-action automatically replaced invalid tag-character sequences with - as documented in its tag sanitization behavior, so preserve equivalent sanitization before constructing these tags.

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