Add coverage increments 1–3 tests for preserved C# seams and close remaining #199 coverage gaps - #201

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, actions/setup-dotnet@v4, actions/upload-artifact@v4, microsoft/setup-msbuild@v2, nuget/setup-nuget@v2. Actions will be forced to run with Node.js 24 by default starting June 16th, 2026. Node.js 20 will be removed from the runner on September 16th, 2026. Please check if updated versions of these actions are available that support Node.js 24. To opt into Node.js 24 now, set the FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true environment variable on the runner or in your workflow file. Once Node.js 24 becomes the default, you can temporarily opt out by setting ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION=true. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

'AsyncEnumerable.ForEachAwaitAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource, Task>, CancellationToken)' is obsolete: 'Use the language support for async foreach instead.'

'AsyncEnumerable.ForEachAwaitWithCancellationAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource, CancellationToken, Task>, CancellationToken)' is obsolete: 'Use the language support for async foreach instead.'

'AsyncEnumerable.SelectAwaitWithCancellation<TSource, TResult>(IAsyncEnumerable<TSource>, Func<TSource, CancellationToken, ValueTask<TResult>>)' is obsolete: 'Use Select. IAsyncEnumerable LINQ is now in System.Linq.AsyncEnumerable, and the SelectAwaitWithCancellation functionality now exists as overloads of Select.'

'AsyncEnumerable.ForEachAwaitWithCancellationAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource, CancellationToken, Task>, CancellationToken)' is obsolete: 'Use the language support for async foreach instead.'

'AsyncEnumerable.ForEachAwaitWithCancellationAsync<TSource>(IAsyncEnumerable<TSource>, Func<TSource, CancellationToken, Task>, CancellationToken)' is obsolete: 'Use the language support for async foreach instead.'

'AsyncEnumerable.SelectAwait<TSource, TResult>(IAsyncEnumerable<TSource>, Func<TSource, ValueTask<TResult>>)' is obsolete: 'Use Select. IAsyncEnumerable LINQ is now in System.Linq.AsyncEnumerable, and the SelectAwait functionality now exists as overloads of Select. You will need to modify your callback to take an additional CancellationToken argument.'

The variable 'OlMail' is declared but never used

'AsyncEnumerable.SelectAwait<TSource, TResult>(IAsyncEnumerable<TSource>, Func<TSource, ValueTask<TResult>>)' is obsolete: 'Use Select. IAsyncEnumerable LINQ is now in System.Linq.AsyncEnumerable, and the SelectAwait functionality now exists as overloads of Select. You will need to modify your callback to take an additional CancellationToken argument.'

Field 'SvgImageSelector._absoluteImagePath' is never assigned to, and will always have its default value null