style(UI): 统一组件圆角样式

Modal:
- 圆角从 rounded-xl 调整为 rounded-md

ToolsDropdown:
- 按钮样式简化，移除条件样式
- 下拉菜单和列表项圆角统一为 rounded-md

src/components/features/ToolsDropdown.tsx

@@ -47,12 +47,7 @@ export function ToolsDropdown({ tools, onToolToggle, onEnableAllToggle }: ToolsD
         <Tooltip content="工具" position="top">
           <button
             onClick={() => setIsOpen(!isOpen)}
-            className={cn(
-              'w-8 h-8 flex items-center justify-center rounded-lg transition-colors cursor-pointer',
-              enabledCount > 0
-                ? 'text-[var(--color-primary)] bg-[var(--color-primary-light)]'
-                : 'text-[var(--color-text-tertiary)] hover:bg-[var(--color-bg-hover)] hover:text-[var(--color-text-secondary)]'
-            )}
+            className="w-8 h-8 flex items-center justify-center rounded-md transition-colors cursor-pointer text-[var(--color-text-tertiary)] hover:bg-[var(--color-bg-hover)] hover:text-[var(--color-text-secondary)]"
           >
             <Wrench size={20} />
           </button>
@@ -67,7 +62,7 @@ export function ToolsDropdown({ tools, onToolToggle, onEnableAllToggle }: ToolsD
       {/* 下拉菜单 */}
       <div
         className={cn(
-          'absolute bottom-full left-0 mb-2 min-w-[220px] bg-[var(--color-bg-primary)] border border-[var(--color-border)] rounded-xl shadow-lg p-2 z-50',
+          'absolute bottom-full left-0 mb-2 min-w-[220px] bg-[var(--color-bg-primary)] border border-[var(--color-border)] rounded-md shadow-lg p-2 z-50',
           'transition-all duration-150',
           isOpen
             ? 'opacity-100 visible translate-y-0'
@@ -87,7 +82,7 @@ export function ToolsDropdown({ tools, onToolToggle, onEnableAllToggle }: ToolsD
             <button
               key={tool.id}
               onClick={() => onToolToggle(tool.id)}
-              className="flex items-center gap-3 w-full px-3 py-2 rounded-lg hover:bg-[var(--color-bg-hover)] transition-colors"
+              className="flex items-center gap-3 w-full px-3 py-2 rounded-md hover:bg-[var(--color-bg-hover)] transition-colors"
             >
               {Icon && <Icon size={20} className="text-[var(--color-text-tertiary)]" />}
               <span className="flex-1 text-sm text-[var(--color-text-primary)] text-left">

src/components/ui/Modal.tsx

@@ -87,7 +87,7 @@ export function Modal({
       <div
         ref={contentRef}
         className={cn(
-          'relative bg-[var(--color-bg-primary)] rounded-xl shadow-2xl',
+          'relative bg-[var(--color-bg-primary)] rounded-md shadow-2xl',
           'animate-scale-in-fast',
           fullScreen ? 'w-full h-full rounded-none' : 'max-h-[90vh]',
           className