🎨 style(settings/ai): 统一设置中心与 AI 配置交互

- 移除设置导航、详情页和 AI 配置列表的冗余分隔线
- 梳理外观字号项顺序并精简日志目录重复标题
- 恢复安全与上下文选项语义色，统一供应商操作按钮
- 强化 MCP 页签、客户端选中态和折叠交互
- 拆分推荐流程与内置工具视图并补齐六语回归测试

frontend/src/utils/aiSettingsPresetLayout.test.ts

@@ -14,13 +14,13 @@ describe('ai settings preset layout', () => {
       display: 'grid',
       gridTemplateColumns: 'repeat(2, minmax(0, 1fr))',
       columnGap: 12,
-      rowGap: 0,
+      rowGap: 2,
       gridAutoRows: '58px',
       alignItems: 'stretch',
     });
   });
 
-  it('stretches each provider choice to fill the row without rounded-card decoration', () => {
+  it('stretches each provider choice to fill the row with only a subtle selection radius', () => {
     expect(PROVIDER_PRESET_CARD_BASE_STYLE).toMatchObject({
       display: 'flex',
       alignItems: 'center',
@@ -28,7 +28,7 @@ describe('ai settings preset layout', () => {
       height: '100%',
       minHeight: '58px',
       overflow: 'hidden',
-      borderRadius: 0,
+      borderRadius: 4,
       textAlign: 'left',
     });
   });

frontend/src/utils/aiSettingsPresetLayout.ts

@@ -6,7 +6,7 @@ export const PROVIDER_PRESET_GRID_STYLE: CSSProperties = {
   display: 'grid',
   gridTemplateColumns: 'repeat(2, minmax(0, 1fr))',
   columnGap: 12,
-  rowGap: 0,
+  rowGap: 2,
   gridAutoRows: `${PROVIDER_PRESET_CARD_HEIGHT}px`,
   alignItems: 'stretch',
 };
@@ -14,7 +14,7 @@ export const PROVIDER_PRESET_GRID_STYLE: CSSProperties = {
 export const PROVIDER_PRESET_CARD_BASE_STYLE: CSSProperties = {
   width: '100%',
   padding: '9px 10px',
-  borderRadius: 0,
+  borderRadius: 4,
   border: 'none',
   cursor: 'pointer',
   transition: 'background-color 0.16s ease, border-color 0.16s ease',