parallelized matrix build

[bitfaster]

No description provided.

[coveralls]

coverage: 98.986% (-0.03%) from 99.02%
when pulling 94e97fb on users/alexpeck/buildall
into 019070a on main.

[Copilot]

Pull Request Overview

This PR refactors the existing separate OS jobs into a single parallelized matrix build, unifying steps and parameterizing test, coverage, and artifact uploads.

• Introduces a matrix strategy to run multiple framework/OS combos in parallel
• Consolidates test and artifact upload steps using matrix variables and a bash script
• Parameterizes coveralls publishing and NuGet artifact upload per matrix entry

Comments suppressed due to low confidence (2)

.github/workflows/gate.yml:16

• The continue-on-error key is only valid on steps, not at the job level. If you want the matrix to continue after a failure, replace this with strategy.fail-fast: false under strategy.

    continue-on-error: true

.github/workflows/gate.yml:112

• The upload step for .NET Std runs only when matrix.std is true but lacks if: success() || failure(), so artifacts won’t be uploaded if tests fail. Add that condition to ensure results are always captured.

        if: ${{ matrix.std }}