refactor: reorganize directory structure into src/

Move all source code directories into src/ for cleaner project structure:
- pages/, components/, utils/, config/, providers/, types/, lib/, assets/, entrypoints/ → src/
- Use WXT srcDir config to resolve @/ alias to src/
- Update tsconfig, vitest, eslint, tailwind configs
- Remove scattered README.md files from subdirectories
- Update documentation (AGENTS.md, CODING_STANDARDS.md, README.md)
- Fix pre-existing lint error in RouterProvider.tsx

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/components/__tests__/PageSkeleton.test.tsx

@@ -0,0 +1,64 @@
+import { describe, expect, it } from 'vitest';
+import { render } from '@testing-library/react';
+import PageSkeleton from '@/components/PageSkeleton';
+
+describe('PageSkeleton 组件', () => {
+  describe('渲染测试', () => {
+    it('默认应渲染 dashboard 骨架屏', () => {
+      const { container } = render(<PageSkeleton />);
+
+      // dashboard 骨架屏包含 6 个卡片
+      const cards = container.querySelectorAll('.rounded-xl');
+      expect(cards.length).toBe(6);
+    });
+
+    it('variant 为 dashboard 时应渲染仪表盘卡片骨架', () => {
+      const { container } = render(<PageSkeleton variant="dashboard" />);
+
+      // 每个卡片有 2 个骨架元素（图标、文本），6 个卡片共 12 个
+      const cards = container.querySelectorAll('.rounded-xl');
+      expect(cards.length).toBe(6);
+    });
+
+    it('variant 为 tool 时应渲染工具页面骨架', () => {
+      const { container } = render(<PageSkeleton variant="tool" />);
+
+      // tool 骨架屏包含标题、输入区、控制栏 3 个按钮、结果区
+      const skeletons = container.querySelectorAll('.animate-pulse');
+      expect(skeletons.length).toBeGreaterThan(0);
+    });
+  });
+
+  describe('布局结构测试', () => {
+    it('dashboard 骨架屏应使用 grid 布局', () => {
+      const { container } = render(<PageSkeleton variant="dashboard" />);
+      const gridContainer = container.firstChild as HTMLElement;
+
+      expect(gridContainer).toHaveClass('grid');
+    });
+
+    it('tool 骨架屏应有内边距', () => {
+      const { container } = render(<PageSkeleton variant="tool" />);
+      const toolContainer = container.firstChild as HTMLElement;
+
+      expect(toolContainer).toHaveClass('p-5');
+    });
+  });
+
+  describe('骨架屏元素测试', () => {
+    it('dashboard 骨架屏应包含圆角和边框样式', () => {
+      const { container } = render(<PageSkeleton variant="dashboard" />);
+
+      // 获取第一个卡片容器
+      const card = container.querySelector('.rounded-xl.border');
+      expect(card).toBeInTheDocument();
+    });
+
+    it('tool 骨架屏应包含动画脉冲效果', () => {
+      const { container } = render(<PageSkeleton variant="tool" />);
+
+      const skeletons = container.querySelectorAll('.animate-pulse');
+      expect(skeletons.length).toBeGreaterThan(0);
+    });
+  });
+});