6944db8ab4
Core MainViewModel.cs 758 -> 495 lines. Moved the source add/remove/image block (AddSource, NextSourceName, AddImage, BuildImageCandidates, PickImageBytes, AddAsset, AddImageSource, AddReusedImage, RemoveElement) into a new MainViewModel.Sources.cs partial, and WebView2 source hosting (RegisterLoadedWebSources, InitWebView2, OnWebView2PreviewBitmapChanged) into a new MainViewModel.Web.cs partial. Pruned now-dead usings from core. Zero behavior change; build 0 warnings; 246 pass, only the 2 known failures. Docs: ViewModels/index.md Phase 3 tracker updated in same commit.