feat: enhance layer mask handling and opacity management

- Introduced `getLayerMask` utility to streamline layer mask retrieval.
- Updated layer rendering logic to incorporate layer masks and opacity adjustments.
- Added functionality to prevent dropping a group into its descendants.
- Enhanced image texture rendering to support opacity parameters across various rendering functions.
- Implemented group layer bounds application for better scaling and positioning.
- Added tests to ensure correct behavior when handling layer masks and group layers.
- Created new types for asset generation provenance to track generated assets more effectively.

core/index.ts

@@ -1,5 +1,6 @@
 export type { Artboard } from "./artboard";
 export type { Asset } from "./asset";
+export type { AssetGenerationProvenance, AssetProvenance, GeneratedAssetAcceptance, GeneratedAssetMode } from "./asset-provenance";
 export type { BaseLayer, LayerClippingMask } from "./base-layer";
 export type { ImageDocument } from "./document";
 export type {
@@ -15,5 +16,7 @@ export type {
 export type { ArtboardId, AssetId, DocumentId, LayerId } from "./id";
 export type { ImageLayer } from "./image-layer";
 export type { Layer } from "./layer";
+export type { LayerMask } from "./layer-mask";
+export { getLayerMask, hasLayerMask } from "./layer-mask-utils";
 export type { LayerGroup } from "./layer-group";
 export type { RasterLayer } from "./raster-layer";