v1.4.0 - Major bug fixes, HEMG double-tail support, and code refactoring

🐛 Bug Fixes (10 items)

• Fix LoadMeanFromFile using wrong path → now uses GetDailyOutputDirectory()
• Fix ApplyThresholding using RMS instead of mean-centered std dev
• Fix ProcessData not checking SelectedMode for file-based mean loading
• Fix histogram range hardcoded to 0-16383 even after baseline subtraction
• Fix nullable warnings (CS8618/CS8622) on RequestPlotUpdate and _cts
• Fix HEMG erfc formula errors in both left and right tails → (σ/τ − Δx/σ) / √2
• Fix HEMG tau parameters not scaled to sigma units (caused exp overflow)
• Fix HEMG fitCurve length mismatch with caller's binCenters
• Fix ChannelViewModel stats annotation using wrong coordinate system
• Fix FitCurve/BinCenters length guard missing

✨ New Features

• Hyper-EMG double tail — added as 3rd fit method option (Gaussian / Single / Double)
• Adaptive gradient descent — new optimizer with line search + central difference
• Fit window ±5σ — fit only bins near peak for better speed & stability

♻️ Refactoring

• Extract 5 shared helpers: GetLayerSelector, ExtractChannelData, ApplyBaselineSubtraction, BuildHistogram, CalculateMean
• Remove duplicated code: layerSelector (4→1), baseline (2→1), histogram (2→1)
• Remove unused AccordFittingService.cs + Accord.Math/Accord.Statistics NuGet packages
• Remove dead code: InterpolateFitCurve, PerformFit, createMarkerShape
• Remove empty folders: Infrastructure/, Presentation/
• RefreshChannelPlots() reduced from ~70 → ~25 lines
• ProcessData Parallel.For body reduced from ~70 → ~25 lines
• Net -38 lines (324 added, 362 removed)

📊 Build

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