ci(codecov): wait for all coverage uploads before reporting status

[sandersaares]

The coverage job in main.yml runs a 3-OS matrix (ubuntu-latest, windows-latest, ubuntu-24.04-arm), each uploading coverage to Codecov independently. Codecov posted the codecov/project status as soon as the first upload arrived, before data from the other platforms had been received, which flagged us with a spurious "coverage check failed".

This sets codecov.notify.after_n_builds: 3 so Codecov holds the status until all coverage matrix jobs have uploaded and it has the full multi-platform dataset. Each matrix OS does a single upload (its comma-separated lcov files are merged into one report), so the value equals the number of OS entries in the matrix.

I added cross-referencing comments in both codecov.yml and the matrix in main.yml so maintainers keep the count in sync when adding/removing an OS.

Note: with after_n_builds: 3, if one coverage leg fails it uploads fewer than 3 reports and the status stays pending, blocking merge. This is acceptable since coverage is already a required check, so a failing leg must be fixed/re-run regardless.

The config was validated against https://codecov.io/validate (Valid!).

[Copilot]

Pull request overview

Adjusts Codecov configuration so the codecov/project status isn’t reported until all OS legs of the coverage matrix have uploaded coverage, preventing premature/spurious failures on PRs.

Changes:

• Add codecov.notify.after_n_builds: 3 to delay status reporting until all three matrix uploads arrive.
• Add cross-referencing comments in codecov.yml and the coverage job matrix to keep the build count and OS list in sync.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
codecov.yml	Adds Codecov notify settings to wait for all expected coverage uploads before posting status.
.github/workflows/main.yml	Documents the coupling between the coverage OS matrix size and codecov.notify.after_n_builds.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.9%. Comparing base (963e015) to head (01b8b47).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #497   +/-   ##
=====================================
  Coverage   99.9%   99.9%           
=====================================
  Files        336     336           
  Lines      24829   24829           
=====================================
  Hits       24818   24818           
  Misses        11      11           

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