refactor: remove macOS vibrancy support and unify glass surfaces

Drops the macOS vibrancy toggle, IPC, and related settings copy
Updates dialogs, popovers, tooltips, and dropdowns to use shared glass styles
Adds sticky header fade behavior to model picker and sidebar lists

packages/ui/src/components/views/SettingsWindow.tsx

@@ -38,7 +38,7 @@ export const SettingsWindow: React.FC<SettingsWindowProps> = ({ open, onOpenChan
       <Dialog.Portal>
         <Dialog.Backdrop
           className={cn(
-            'fixed inset-0 z-50 bg-black/50 dark:bg-black/75',
+            'oc-glass-backdrop fixed inset-0 z-50 bg-black/25 dark:bg-black/40',
             'transition-opacity duration-150 ease-out',
             'data-[starting-style]:opacity-0 data-[ending-style]:opacity-0',
           )}
@@ -50,7 +50,7 @@ export const SettingsWindow: React.FC<SettingsWindowProps> = ({ open, onOpenChan
               'relative pointer-events-auto',
               'w-[90vw] max-w-[1200px] h-[85vh] max-h-[900px]',
               'rounded-xl border shadow-none overflow-hidden origin-center',
-              'bg-background',
+              'oc-glass-dialog',
               'transition-all duration-150 ease-out',
               'data-[starting-style]:opacity-0 data-[starting-style]:scale-[0.98]',
               'data-[ending-style]:opacity-0 data-[ending-style]:scale-[0.98]',