/* ===================================
   GAME PANEL - Universal Panel System
   ===================================
   
   Behavioral styles only. Visual styling (colors, borders, backgrounds)
   stays in each panel's own CSS file (character-sheet.css, artificer.css, etc).
   
   GamePanel.js handles:
   - Click-vs-drag on title bars
   - Scroll isolation (wheel events)
   - Z-index focus management
   - ESC to close topmost panel
   
   Each panel keeps its own:
   - Collapsed/expanded CSS transitions
   - Background gradients, borders, colors
   - Content layout and typography
   ===================================  */