Brush - Enhancement

Being able to create brush from already drawn pixel and apply it while mouse moving.

Save brushes for future usage.

Save in the project or aside to be reused for other projects.

The issue does not name files, tests, or entry points. Start by locating the existing drawing and project-save flows, then define how creating, applying, and persisting reusable brushes should work before implementation; done means brushes can be created from drawn pixels, applied while moving the mouse, and reused within or across projects.

Written by the indexing model from the issue text.