Add configurable ProForma residue validation - #120

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-dotnet@v4, codecov/codecov-action@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Non-nullable field '_elementProvider' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

'IIsotopicDistribution.CreateChargedDistribution(int, bool)' is obsolete: 'Use CreateChargedDistribution(int charge, double chargeCarrier) instead.'

Nullable value type may be null.

Nullable value type may be null.

Possible null reference return.

Possible null reference return.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.