feat(gui): add Design Token system and theme configuration (U1)

- Create tokens.css with CSS custom properties for colors, spacing,
  radius, fonts, shadows, transitions, and code theme
- Create theme.ts mapping tokens to Ant Design Vue ConfigProvider
- Create styles/index.ts as unified entry point
- Inject theme into App.vue ConfigProvider
- Import styles in main.ts

Primary color unified to #7c3aed (purple gradient brand color).

src/agentkit/server/frontend/src/App.vue

@@ -1,5 +1,5 @@
 <template>
-  <a-config-provider :locale="zhCN">
+  <a-config-provider :locale="zhCN" :theme="themeConfig">
     <AppLayout />
   </a-config-provider>
 </template>
@@ -8,6 +8,7 @@
 import { ConfigProvider as AConfigProvider } from 'ant-design-vue'
 import zhCN from 'ant-design-vue/es/locale/zh_CN'
 import AppLayout from './components/layout/AppLayout.vue'
+import { themeConfig } from './styles'
 </script>
 
 <style>

src/agentkit/server/frontend/src/main.ts

@@ -1,6 +1,7 @@
 import { createApp } from 'vue'
 import { createPinia } from 'pinia'
 import 'ant-design-vue/dist/reset.css'
+import './styles'
 import App from './App.vue'
 import router from './router'
 

src/agentkit/server/frontend/src/styles/index.ts

@@ -0,0 +1,8 @@
+/**
+ * Fischer AgentKit Styles Entry
+ *
+ * Import this module to load all design tokens and theme configuration.
+ */
+
+import './tokens.css'
+export { themeConfig } from './theme'

src/agentkit/server/frontend/src/styles/theme.ts

@@ -0,0 +1,81 @@
+/**
+ * Ant Design Vue Theme Token Mapping
+ *
+ * Maps CSS custom properties to Ant Design Vue ConfigProvider theme tokens.
+ * This ensures antd components use the same design tokens as custom components.
+ */
+
+import type { ThemeConfig } from 'ant-design-vue/es/config-provider/context'
+
+export const themeConfig: ThemeConfig = {
+  token: {
+    // Brand
+    colorPrimary: '#7c3aed',
+    colorInfo: '#7c3aed',
+
+    // Semantic
+    colorSuccess: '#10b981',
+    colorWarning: '#f59e0b',
+    colorError: '#ef4444',
+
+    // Text
+    colorText: '#171717',
+    colorTextSecondary: '#525252',
+    colorTextTertiary: '#737373',
+    colorTextQuaternary: '#a3a3a3',
+
+    // Background
+    colorBgContainer: '#ffffff',
+    colorBgLayout: '#fafafa',
+    colorBgElevated: '#ffffff',
+
+    // Border
+    colorBorder: '#e5e5e5',
+    colorBorderSecondary: '#f0f0f0',
+
+    // Font
+    fontSize: 14,
+    fontSizeSM: 12,
+    fontSizeLG: 16,
+    fontSizeXL: 20,
+
+    // Radius
+    borderRadius: 8,
+    borderRadiusSM: 6,
+    borderRadiusLG: 12,
+
+    // Spacing
+    marginXS: 4,
+    marginSM: 8,
+    margin: 16,
+    marginMD: 16,
+    marginLG: 24,
+    marginXL: 32,
+
+    // Shadow
+    boxShadow: '0 1px 2px 0 rgba(0, 0, 0, 0.05)',
+    boxShadowSecondary: '0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05)',
+
+    // Control
+    controlHeight: 32,
+    controlHeightSM: 24,
+    controlHeightLG: 40,
+  },
+  components: {
+    Menu: {
+      itemSelectedBg: '#ede9fe',
+      itemSelectedColor: '#7c3aed',
+      itemHoverBg: '#f5f3ff',
+      itemHoverColor: '#7c3aed',
+      itemColor: '#525252',
+    } as Record<string, unknown>,
+    Tabs: {
+      itemSelectedColor: '#7c3aed',
+      itemHoverColor: '#6d28d9',
+    } as Record<string, unknown>,
+    Select: {
+      colorPrimary: '#7c3aed',
+      colorPrimaryHover: '#6d28d9',
+    } as Record<string, unknown>,
+  },
+}

src/agentkit/server/frontend/src/styles/tokens.css

@@ -0,0 +1,136 @@
+/**
+ * Fischer AgentKit Design Tokens
+ *
+ * CSS Custom Properties as the single source of truth.
+ * Ant Design Vue theme tokens are mapped from these values in theme.ts.
+ */
+
+:root {
+  /* ── Brand Colors ── */
+  --color-primary: #7c3aed;
+  --color-primary-hover: #6d28d9;
+  --color-primary-active: #5b21b6;
+  --color-primary-light: #ede9fe;
+  --color-primary-bg: #f5f3ff;
+
+  /* ── Gradient ── */
+  --gradient-brand: linear-gradient(135deg, #7c3aed 0%, #1e1b4b 100%);
+
+  /* ── Semantic Colors ── */
+  --color-success: #10b981;
+  --color-success-light: #d1fae5;
+  --color-warning: #f59e0b;
+  --color-warning-light: #fef3c7;
+  --color-error: #ef4444;
+  --color-error-light: #fee2e2;
+  --color-info: #3b82f6;
+  --color-info-light: #dbeafe;
+
+  /* ── Neutral / Gray Scale ── */
+  --color-gray-50: #fafafa;
+  --color-gray-100: #f5f5f5;
+  --color-gray-200: #e5e5e5;
+  --color-gray-300: #d4d4d4;
+  --color-gray-400: #a3a3a3;
+  --color-gray-500: #737373;
+  --color-gray-600: #525252;
+  --color-gray-700: #404040;
+  --color-gray-800: #262626;
+  --color-gray-900: #171717;
+
+  /* ── Background ── */
+  --bg-primary: #ffffff;
+  --bg-secondary: #fafafa;
+  --bg-tertiary: #f5f5f5;
+  --bg-elevated: #ffffff;
+  --bg-code: #282c34;
+
+  /* ── Foreground / Text ── */
+  --text-primary: #171717;
+  --text-secondary: #525252;
+  --text-tertiary: #737373;
+  --text-placeholder: #a3a3a3;
+  --text-inverse: #ffffff;
+  --text-code: #abb2bf;
+
+  /* ── Border ── */
+  --border-color: #e5e5e5;
+  --border-color-hover: #d4d4d4;
+  --border-color-active: var(--color-primary);
+  --border-color-split: #f0f0f0;
+
+  /* ── Spacing ── */
+  --space-1: 4px;
+  --space-2: 8px;
+  --space-3: 12px;
+  --space-4: 16px;
+  --space-5: 20px;
+  --space-6: 24px;
+  --space-8: 32px;
+  --space-10: 40px;
+  --space-12: 48px;
+
+  /* ── Border Radius ── */
+  --radius-sm: 4px;
+  --radius-md: 6px;
+  --radius-lg: 8px;
+  --radius-xl: 12px;
+  --radius-full: 9999px;
+
+  /* ── Font Size ── */
+  --font-xs: 12px;
+  --font-sm: 13px;
+  --font-base: 14px;
+  --font-md: 16px;
+  --font-lg: 20px;
+  --font-xl: 24px;
+
+  /* ── Font Weight ── */
+  --font-weight-normal: 400;
+  --font-weight-medium: 500;
+  --font-weight-semibold: 600;
+  --font-weight-bold: 700;
+
+  /* ── Line Height ── */
+  --leading-tight: 1.25;
+  --leading-normal: 1.5;
+  --leading-relaxed: 1.75;
+
+  /* ── Shadow ── */
+  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
+  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
+  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
+  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
+
+  /* ── Transition ── */
+  --transition-fast: 150ms ease;
+  --transition-normal: 200ms ease;
+  --transition-slow: 300ms ease;
+
+  /* ── Z-Index ── */
+  --z-dropdown: 1000;
+  --z-sticky: 1020;
+  --z-fixed: 1030;
+  --z-modal-backdrop: 1040;
+  --z-modal: 1050;
+  --z-popover: 1060;
+  --z-tooltip: 1070;
+
+  /* ── Layout ── */
+  --topnav-height: 48px;
+  --sidebar-width: 280px;
+  --quadrant-min-size: 320px;
+
+  /* ── Code Theme (One Dark Pro) ── */
+  --code-bg: #282c34;
+  --code-fg: #abb2bf;
+  --code-keyword: #c678dd;
+  --code-string: #98c379;
+  --code-number: #d19a66;
+  --code-comment: #5c6370;
+  --code-function: #61afef;
+  --code-variable: #e06c75;
+  --code-type: #e5c07b;
+  --code-added-bg: rgba(16, 185, 129, 0.15);
+  --code-removed-bg: rgba(239, 68, 68, 0.15);
+}