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/state.ts

@@ -1,7 +1,7 @@
 import type { ImageDocument } from "@core/document";
-import type { Angle, Size, Vec2D } from "@core/geometry";
+import type { Angle, Rect, Size, Transform, Vec2D } from "@core/geometry";
 import type { ArtboardId, AssetId, LayerId } from "@core/id";
-import type { ToolState } from "./tools";
+import type { GenerateSettings, ToolState } from "./tools";
 import type { TransformSession } from "./transform";
 
 export type ViewportState = {
@@ -34,10 +34,61 @@ export type BrushStrokePreviewState = {
   source: string;
 };
 
+export type GenerationCandidate = {
+  id: string;
+  source: string;
+  mimeType: string;
+  intrinsicSize: Size;
+  mode: GenerateSettings["mode"];
+  settings: GenerateSettings;
+  seed: number;
+  width: number;
+  height: number;
+  inputImage?: string;
+  maskImage?: string;
+  placement: {
+    artboardId: ArtboardId;
+    layerName: string;
+    transform: Transform;
+  };
+  inpaint?: {
+    targetLayerId: LayerId;
+    maskLayerId: LayerId;
+    sourceAssetId: AssetId;
+    maskAssetId: AssetId;
+    inputImage: string;
+    maskImage: string;
+    crop: {
+      assetBounds: Rect;
+      documentBounds: Rect;
+      padding: number;
+      maskedAreaOnly: boolean;
+    };
+    mask: {
+      polarity: GenerateSettings["inpaint"]["maskPolarity"];
+      activeBounds: Rect;
+    };
+    backend: {
+      growMaskBy: number;
+      maskedContent: GenerateSettings["inpaint"]["maskedContent"];
+      maskBlur: number;
+      maskFeather: number;
+      maskExpand: number;
+      cropPadding: number;
+    };
+  };
+};
+
+export type GenerationState = {
+  candidates: GenerationCandidate[];
+  selectedCandidateId?: string;
+};
+
 export type EditorState = {
   viewport: ViewportState;
   selection: SelectionState;
   tools: ToolState;
+  generation: GenerationState;
   transformSession?: TransformSession;
   maskEdit?: MaskEditState;
   brushPreview?: BrushPreviewState;