Develop (#55)

feat: optimize dashboard/search UX and simplify extension architecture

Redesign Dashboard with compact tool grid and recently used tools
Improve TopBar search UX with Cmd/Ctrl+K shortcut and better history navigation
Reorganize project structure into src/
Migrate i18n from react-i18next to chrome.i18n
Remove runtime language switch and settings page
Remove HTML/Markdown conversion tools
Clean up unused code, dead animations, redundant comments, and imports
Improve component consistency with shadcn/ui patterns
Replace hardcoded strings/colors with i18n tokens and theme tokens
Add comprehensive project documentation and coding standards
Fix CI artifact upload workflow and multiple TypeScript/test issues

Includes various refactors, UI polish, i18n cleanup, CI improvements,
and maintenance updates across the codebase.

src/utils/__tests__/textStatistics.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from 'vitest';
+import { formatByteSize, getTextStats } from '@/utils/textStatistics';
+
+describe('textStatistics utils', () => {
+  describe('getTextStats', () => {
+    it('should return zeros for empty text', () => {
+      const stats = getTextStats('');
+      expect(stats).toEqual({ characters: 0, words: 0, lines: 0, bytes: 0 });
+    });
+
+    it('should count characters correctly', () => {
+      expect(getTextStats('abc').characters).toBe(3);
+      expect(getTextStats('a b c').characters).toBe(5);
+      expect(getTextStats('你好').characters).toBe(2);
+    });
+
+    it('should count English words correctly', () => {
+      expect(getTextStats('hello world').words).toBe(2);
+      expect(getTextStats('  hello   world  ').words).toBe(2);
+      expect(getTextStats('hello, world!').words).toBe(2);
+    });
+
+    it('should count Chinese words correctly', () => {
+      // "你好世界" 在 Intl.Segmenter 中通常被识别为 "你好" 和 "世界" 两个词
+      const stats = getTextStats('你好世界');
+      expect(stats.words).toBe(2);
+    });
+
+    it('should count mixed language words correctly', () => {
+      const stats = getTextStats('Hello 你好');
+      // "Hello" (1) + "你好" (1) = 2
+      expect(stats.words).toBe(2);
+    });
+
+    it('should count lines correctly', () => {
+      expect(getTextStats('line1\nline2').lines).toBe(2);
+      expect(getTextStats('line1\nline2\n').lines).toBe(3);
+    });
+
+    it('should count bytes correctly (UTF-8)', () => {
+      expect(getTextStats('abc').bytes).toBe(3);
+      expect(getTextStats('你好').bytes).toBe(6); // UTF-8 中每个常用汉字占 3 字节
+    });
+
+    it('should handle special cases', () => {
+      expect(getTextStats('   ').words).toBe(0);
+      expect(getTextStats('\n\n\n').lines).toBe(4);
+      expect(getTextStats('\n\n\n').words).toBe(0);
+    });
+  });
+
+  describe('formatByteSize', () => {
+    it('should format bytes correctly', () => {
+      expect(formatByteSize(100)).toBe('100 B');
+      expect(formatByteSize(0)).toBe('0 B');
+      expect(formatByteSize(1024)).toBe('1.0 KB');
+      expect(formatByteSize(1024 * 1024)).toBe('1.00 MB');
+    });
+  });
+});