feat(ui): improve theme consistency and add diff panel shortcut

packages/ui/src/components/chat/FileMentionAutocomplete.tsx

@@ -234,7 +234,7 @@ export const FileMentionAutocomplete = React.forwardRef<FileMentionHandle, FileM
   return (
       <div
         ref={containerRef}
-        className="absolute z-[100] min-w-0 w-full max-w-[520px] max-h-64 bg-popover border border-border rounded-xl shadow-none bottom-full mb-2 left-0 flex flex-col"
+        className="absolute z-[100] min-w-0 w-full max-w-[520px] max-h-64 bg-background border border-border rounded-xl shadow-none bottom-full mb-2 left-0 flex flex-col"
       >
         <ScrollableOverlay outerClassName="flex-1 min-h-0" className="px-0">
         {loading ? (
@@ -255,7 +255,7 @@ export const FileMentionAutocomplete = React.forwardRef<FileMentionHandle, FileM
                   ref={(el) => { itemRefs.current[index] = el; }}
                   className={cn(
                     "flex items-center gap-2 px-3 py-1.5 cursor-pointer typography-ui-label rounded-lg",
-                    isSelected && "bg-accent"
+                    isSelected && "bg-muted"
                   )}
                   onClick={() => handleFileSelect(file)}
                   onMouseEnter={() => setSelectedIndex(index)}