Replaces the single large mask canvas with a chunked system, where mask data is stored in 512x512 pixel chunks. Updates all mask drawing, compositing, and manipulation logic to operate on these chunks, improving performance and scalability for large or sparse masks. The active mask canvas is now a composite of all non-empty chunks, and all mask operations (drawing, setting, clearing) are adapted to the new chunked architecture.
This update introduces a unified output area bounds system, allowing the output area to be extended in all directions independently of the custom shape. All mask and layer operations now reference outputAreaBounds, ensuring correct alignment and rendering. The mask tool, mask editor, and export logic have been refactored to use these bounds, and a new UI for output area extension with live preview and tooltips has been added. The code also improves logging and visualization of mask and output area boundaries.
