Fix blocked Coveralls upload by splitting main coverage workflow

[harryswift01]

Summary

This PR separates pull request validation from the Coveralls baseline upload workflow. The previous workflow attempted to support both PR checks and push to main coverage uploads in the same file, but the Coveralls upload was still blocked because it depended on PR-only jobs.

Changes

Split PR CI and Coveralls workflows:

• Replaced the combined PR/push workflow with two separate workflows:
  • Pull request CI for tests, docs, pre-commit, regression checks, and PR coverage reporting.
  • Coveralls Main for rebuilding the main branch coverage baseline on push to main.
• Removed the push trigger from the PR CI workflow.
• Added a dedicated coveralls-main.yaml workflow that runs independently on pushes to main.
• Added manual workflow_dispatch support so the Coveralls baseline can be rebuilt manually when required.

Restore Coveralls coverage reporting:

• Keeps PR coverage uploads to Coveralls so coverage changes can be checked during review.
• Adds a dedicated main branch Coveralls upload to maintain the baseline used for PR coverage comparisons.
• Keeps coverage generation through pytest-cov and coverage.xml.

Impact

• Restores Coveralls uploads on push to main.
• Ensures the main branch coverage baseline is rebuilt after merges.
• Allows PRs to be checked against the latest main coverage baseline.
• Avoids skipped-job dependency issues caused by mixing PR-only and push-to-main logic in one workflow.

[jimboid]

Looks like this PR will fix the issue described.