ci: add release workflow

[Maxerns]

Summary

• validate empty, floating, partial, prerelease and missing release versions
• reuse the full target matrix before publishing an action release
• create versioned releases and move only the matching major tag
• require release tags to point to commits on main

Testing

• checked both workflows with actionlint
• checked YAML syntax
• tested the release tag parser
• tested the main ancestry check

[Maxerns]

Replaced by #7 after removing the release workflow and narrowing the change to failure-path coverage.