Add codecov configuration for coverage reporting

[fain182]

Summary

This PR adds a codecov.yml configuration file to establish coverage reporting standards and CI integration for the project.

Key Changes

• Coverage precision and range: Set coverage display to 2 decimal places with a range of 70-100%
• Project coverage requirements: Allow up to 1% coverage drop per PR with auto-target detection
• Patch coverage requirements: Enforce 80% coverage on new/changed lines with 5% tolerance
• CI integration: Configure codecov to wait for CI to pass and consolidate coverage uploads before computing status
• Comment behavior: Update existing PR comments instead of posting new ones on each push
• Exclusions: Exclude test files, examples, and bin directories from coverage calculations

Implementation Details

The configuration uses a balanced approach to coverage enforcement:

• Project-level checks are lenient (1% threshold) to avoid blocking on minor coverage gaps
• Patch-level checks are stricter (80% target) to maintain quality on new code
• CI failures are treated as errors to prevent false positives from incomplete reports
• Test and example code are excluded from coverage metrics to focus on production code quality

https://claude.ai/code/session_01V8XmVe48bhQkjeNRmGSm6n

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.29%. Comparing base (c5705ee) to head (3a9ecc9).

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #618   +/-   ##
=========================================
  Coverage     98.29%   98.29%           
  Complexity      696      696           
=========================================
  Files            87       87           
  Lines          1991     1991           
=========================================
  Hits           1957     1957           
  Misses           34       34           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[AlessandroMinoccheri]

LGTM 👍