fix/SaveLastOpenFilesList() - #692

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, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

The type name AutoColumnizer conflicts in whole or in part with the namespace name 'AutoColumnizer'. Change either name to eliminate the conflict. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1724)

Modify 'PlaySystemBeep' to catch a more specific allowed exception type, or rethrow the exception (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1031)

The type name Extensions conflicts in whole or in part with the namespace name 'ColumnizerLib.Extensions'. Change either name to eliminate the conflict. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1724)

In externally visible method 'string TextValueSpanExtensions.GetText(ILogLine logLine)', validate parameter 'logLine' is non-null before using it. If appropriate, throw an 'ArgumentNullException' when the argument is 'null'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1062)

In externally visible method 'string TextValueSpanExtensions.GetText(IColumn column)', validate parameter 'column' is non-null before using it. If appropriate, throw an 'ArgumentNullException' when the argument is 'null'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1062)

Change the type of parameter 'uriString' of method 'IFileSystemPlugin.GetLogfileInfo(string)' from 'string' to 'System.Uri', or provide an overload to 'IFileSystemPlugin.GetLogfileInfo(string)' that allows 'uriString' to be passed as a 'System.Uri' object (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1054)

Change the type of parameter 'uriString' of method 'IFileSystemPlugin.CanHandleUri(string)' from 'string' to 'System.Uri', or provide an overload to 'IFileSystemPlugin.CanHandleUri(string)' that allows 'uriString' to be passed as a 'System.Uri' object (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1054)

Non-nullable property 'Parent' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier, or declaring the property as nullable, or safely handling the case where 'field' is null in the 'get' accessor.

Nullability of type of parameter 'obj' doesn't match overridden member (possibly because of nullability attributes).