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.

input/layers-panel.ts

@@ -3,7 +3,6 @@ import type { Dispatch } from "@commands/dispatcher";
 import type { ImageDocument } from "@core/document";
 import type { ArtboardId, LayerId } from "@core/id";
 import type { Layer } from "@core/layer";
-import type { SelectionState } from "@editor/state";
 import type { KeybindEvent } from "./keyboard";
 
 export type LayerInfo = {
@@ -17,7 +16,12 @@ export type LayerDropTarget = {
   layer: Layer;
 };
 
-export function handleDeleteSelectionKey(options: { event: KeybindEvent; selection: SelectionState; dispatch: Dispatch }): boolean {
+export type DeleteSelectionState = {
+  artboardId?: ArtboardId;
+  layerIds: LayerId[];
+};
+
+export function handleDeleteSelectionKey(options: { event: KeybindEvent; selection: DeleteSelectionState; dispatch: Dispatch }): boolean {
   if (options.event.altKey || options.event.ctrlKey || options.event.metaKey) return false;
   if (options.event.key !== "Backspace" && options.event.key !== "Delete") return false;