fix(linux): stop Wayland GTK drag proxy and PsyDnD ghost (#268)

Block capture-phase dragstart in the webview so stray native HTML5 drags
(e.g. SVG reorder grips) do not create a stuck translucent GTK surface on
Wayland compositors.

Harden PsyDnD lifecycle when mouseup never reaches the webview: blur,
visibilitychange, pointerup/cancel in capture, and Escape cancel the
floating label without dispatching a drop.

Add -webkit-user-drag:none on sidebar customizer grips.

src/styles/components.css

@@ -3232,6 +3232,7 @@
   display: flex;
   align-items: center;
   flex-shrink: 0;
+  -webkit-user-drag: none;
 }
 
 .sidebar-customizer-grip:active {