fix: keep fork quality workflows running

[Onur (onuracar-dev)]

Summary

• skip sticky PR-comment steps for fork pull requests while still running performance and coverage checks
• keep comment publishing non-gating for same-repository pull requests
• include generated Markdown reports alongside raw snapshot artifacts
• add regression coverage for every quality-workflow comment step

The snapshot comparison steps remain fail-closed; only comment publishing uses continue-on-error.

Fixes #522

Testing

• python -B -m unittest discover -s scripts/tests -p 'test_*.py' -v (49 tests)
• cargo fmt --all -- --check
• actionlint .github/workflows/coverage.yml .github/workflows/perf-tests.yml

[Onur (onuracar-dev)]

@microsoft-github-policy-service agree