e5d899d72d
- Implemented a new crate `hcie-watercolor-brushes` containing watercolor brush presets and a procedural splat preview renderer. - Integrated watercolor brushes into the iced GUI's Brushes panel, adding a new category for watercolor brushes. - Updated the `BrushCategory` enum to include `Watercolor` and modified the rendering logic to display watercolor presets. - Added functionality to generate watercolor splat thumbnails using a noise-based algorithm. - Ensured that existing brush styles and engine crates remain unmodified, adhering to project constraints.