fix: resolve theme-switching crash and add automated UI action tests across all tabs - #55

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

Possible null reference argument for parameter 'modelName' in 'double CanIRunItService.ExtractParamBillions(string modelName)'.

Possible null reference argument for parameter 'ModelName' in 'DiffusionFitRequest.DiffusionFitRequest(string ModelName = "Flux.1 Dev", string Quantization = "FP8", int Resolution = 1024, long AvailableVramMb = 16384, long AvailableRamMb = 32768)'.

Possible null reference argument for parameter 'ModelName' in 'VideoFitRequest.VideoFitRequest(string ModelName = "Wan 2.2 14B", string Quantization = "FP8", int FrameCount = 49, int Resolution = 720, long AvailableVramMb = 16384, long AvailableRamMb = 32768)'.

Possible null reference argument for parameter 'modelName' in 'ThreeDFitResult CanIRunItService.Evaluate3DFit(string modelName, long vramMb, long ramMb)'.

Possible null reference argument for parameter 'engineName' in 'AudioFitResult CanIRunItService.EvaluateAudioFit(string engineName, long vramMb, long ramMb)'.

Possible null reference argument for parameter 'ModelName' in 'ThreeDFitResult.ThreeDFitResult(string ModelName, long VramRequiredMb, long RamRequiredMb, FitVerdict FitVerdict, double EstimatedSecondsPerMesh, string RecommendationMessage)'.

Possible null reference argument for parameter 'EngineName' in 'AudioFitResult.AudioFitResult(string EngineName, long VramRequiredMb, long RamRequiredMb, FitVerdict FitVerdict, double EstimatedRealtimeFactor, string RecommendationMessage)'.

Possible null reference argument for parameter 'ModelName' in 'VideoFitResult.VideoFitResult(string ModelName, long DiTModelMb, long FrameContextMb, long VaeDecodeMb, long TotalVramMb, long TotalRamMb, FitVerdict FitVerdict, double EstimatedSecondsPerFrame, string RecommendationMessage)'.

Possible null reference argument for parameter 'ModelName' in 'DiffusionFitResult.DiffusionFitResult(string ModelName, long BaseModelMb, long EncodersMb, long VaeMb, long LatentBufferMb, long TotalVramMb, long TotalRamMb, FitVerdict FitVerdict, double EstimatedSecondsPerImage, string RecommendationMessage)'.