refine editor sheet to floating pill button

- collapsed state: floating pill button in bottom-right corner
- removed panel background when collapsed (transparent)
- violet accent colour to distinguish from shop theme
- white glow outline for visibility on any background
- consistent behaviour on mobile and desktop
- opens to bottom sheet (mobile) or side panel (desktop)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

assets/js/app.js

@@ -700,6 +700,7 @@ const EditorSheet = {
       }
     }
     document.addEventListener("keydown", this._onKeydown)
+
   },
 
   destroyed() {