feat: enhance layer masking functionality and brush controls

- Refactor LayersSheet component to support mask editing state and improve layer visibility handling.
- Introduce functions to collect mask layer IDs and count display layers excluding masks.
- Update BrushControls to include mask view mode options and a Done button for exiting mask editing.
- Modify brush session handling to support brush previews when editing masks.
- Implement a new BrushPreviewRenderer for rendering brush strokes with visual feedback.
- Add document geometry utilities for transforming points and resolving layer bounds.
- Ensure proper cleanup of brush preview on pointer leave and other interactions.

editor/transform-targets.ts

@@ -34,13 +34,19 @@ export function selectedTransformTarget(document: ImageDocument, selection: { ar
 }
 
 function applyLayerBounds(document: ImageDocument, layerId: LayerId, bounds: Rect): ImageDocument {
-  return {
-    ...document,
-    artboards: document.artboards.map((artboard) => ({
-      ...artboard,
-      layers: applyLayerBoundsInTree(document, artboard.layers, layerId, bounds),
-    })),
-  };
+  const layer = findLayer(document, layerId);
+  const targetLayerIds = layer?.clippingMask ? [layerId, layer.clippingMask.maskLayerId] : [layerId];
+
+  return targetLayerIds.reduce(
+    (nextDocument, targetLayerId) => ({
+      ...nextDocument,
+      artboards: nextDocument.artboards.map((artboard) => ({
+        ...artboard,
+        layers: applyLayerBoundsInTree(nextDocument, artboard.layers, targetLayerId, bounds),
+      })),
+    }),
+    document,
+  );
 }
 
 function applyLayerBoundsInTree(document: ImageDocument, layers: Layer[], layerId: LayerId, bounds: Rect): Layer[] {