Configure codecov to not block CI while tracking coverage

[Copilot]

Codecov was configured to fail CI on errors or coverage drops, blocking merge requests. This changes codecov to informational-only mode while maintaining coverage tracking and PR comments.

Changes

• Created .codecov.yml: Sets informational: true for project and patch status checks, preventing codecov from blocking CI based on coverage thresholds
• Updated .github/workflows/ci.yml: Changed fail_ci_if_error: false to prevent CI failures when codecov encounters upload errors

Codecov will continue to post coverage reports and diffs on PRs without affecting merge ability.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.84%. Comparing base (69efb35) to head (c8eb351).
⚠️ Report is 10 commits behind head on relative_trajectory_balance.

Additional details and impacted files

@@                     Coverage Diff                      @@
##           relative_trajectory_balance     #458   +/-   ##
============================================================
  Coverage                        73.84%   73.84%           
============================================================
  Files                               48       48           
  Lines                             7111     7111           
  Branches                           830      830           
============================================================
  Hits                              5251     5251           
  Misses                            1539     1539           
  Partials                           321      321           

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