feat: implement inpainting functionality with mask handling

- Added `createMaskedPixelReplacementSource` function to handle pixel replacement using inpainting.
- Introduced `buildInpaintBundle` to prepare inpainting data including mask generation and validation.
- Created utility functions for mask operations such as `applyMaskedContentModeToRgba`, `expandRectWithinBounds`, and others for mask manipulation.
- Developed tests for inpainting preparation and mask raster utilities to ensure functionality and correctness.
- Implemented mask raster operations including inversion, feathering, blurring, and more.

editor/initial-state.ts

@@ -12,6 +12,10 @@ export const initialEditorState: EditorState = {
     layerIds: [],
   },
   tools: initialToolState,
+  generation: {
+    candidates: [],
+    selectedCandidateId: undefined,
+  },
   transformSession: undefined,
   maskEdit: undefined,
   brushPreview: undefined,