chore(ci): enforce patch coverage for new code only

[stevemilk]

• patch.target: 80% – new code must have ≥80% coverage
• patch.threshold: 0% – prevent patch coverage from dropping
• patch.only_pulls: true – enforce only on PRs

issue: #643

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[0xHansLee]

To enforce pass this before merging the PR, we might need to add this to branch protection rule.