Extract test workflow to a separate CI triggered by pull requests

[yysd5]

Problem

Currently, testing, formatting, and Clippy checks only run during the release process (triggered by tags). This means issues like Clippy warnings are only discovered at the very end, causing release failures.

Solution

• Create a new ci.yml workflow that runs these checks on pull_request and push to main.
• Remove the redundant test job from release.yml.
• This allows using the CI results as a required status check for merging pull requests.

Benefits

• Catch errors early during the PR review process.
• Ensure the main branch is always in a releasable state.
• Faster release process as checks have already passed during PR validation.