refactor: redesign config panels with refined minimal aesthetic (#384)

- Add CSS design system tokens (surfaces, borders, animations) to globals.css
- Update dialog.tsx with rounded-2xl, shadow-dialog, refined close button
- Enhance input.tsx with rounded-xl and refined focus states
- Refactor settings-dialog with SettingItem pattern and consistent control sizing
- Refactor model-config-dialog with ConfigSection/ConfigCard helpers
- Replace emerald-* classes with success design tokens
- Remove unused ValidationButton component and scrollState

components/ui/input.tsx

@@ -8,9 +8,30 @@ function Input({ className, type, ...props }: React.ComponentProps<"input">) {
       type={type}
       data-slot="input"
       className={cn(
-        "file:text-foreground placeholder:text-muted-foreground selection:bg-primary selection:text-primary-foreground dark:bg-input/30 border-input flex h-9 w-full min-w-0 rounded-md border bg-transparent px-3 py-1 text-base shadow-xs transition-[color,box-shadow] outline-none file:inline-flex file:h-7 file:border-0 file:bg-transparent file:text-sm file:font-medium disabled:pointer-events-none disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
-        "focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px]",
-        "aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive",
+        // Base styles
+        "flex h-10 w-full min-w-0 rounded-xl px-3.5 py-2",
+        "border border-border-subtle bg-surface-1",
+        "text-sm text-foreground",
+        // Placeholder
+        "placeholder:text-muted-foreground/60",
+        // Selection
+        "selection:bg-primary selection:text-primary-foreground",
+        // Transitions
+        "transition-all duration-150 ease-out",
+        // Hover state
+        "hover:border-border-default",
+        // Focus state - refined ring
+        "focus:outline-none focus:border-primary focus:ring-2 focus:ring-primary/10",
+        // File input
+        "file:text-foreground file:inline-flex file:h-7 file:border-0",
+        "file:bg-transparent file:text-sm file:font-medium",
+        // Disabled
+        "disabled:pointer-events-none disabled:cursor-not-allowed disabled:opacity-50",
+        // Invalid state
+        "aria-invalid:border-destructive aria-invalid:ring-destructive/20",
+        "dark:aria-invalid:ring-destructive/40",
+        // Dark mode background
+        "dark:bg-surface-1",
         className
       )}
       {...props}