Combine canvas and control panel windows

[ProtonsAndElectrons]

Closes #48.

Summary

• reuse Processing's canvas JFrame as the main Quantum Brush window
• dock the existing control panel and canvas side-by-side in a split pane
• keep the current menus, effect controls, hardware tab, stroke manager entry point, and canvas zoom/pan behavior wired to the same frame

Validation

• javac -cp lib/core-4.4.1.jar -d %TEMP%\quantumbrush-compile-check src\*.java

AI assistance disclosure

I used AI assistance to help inspect the UI flow and draft this patch, then reviewed and validated the resulting change before submitting.