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/textStatistics.ts

@@ -0,0 +1,69 @@
+import { formatBytes } from './format';
+
+/**
+ * 文本统计信息接口
+ */
+export interface TextStats {
+  /** 字符数（包含空格和特殊字符） */
+  characters: number;
+  /** 单词数 */
+  words: number;
+  /** 行数 */
+  lines: number;
+  /** 字节大小 */
+  bytes: number;
+}
+
+/**
+ * 计算文本统计信息
+ *
+ * @param text 输入的文本内容
+ * @returns 统计结果对象
+ */
+export function getTextStats(text: string): TextStats {
+  if (!text) {
+    return { characters: 0, words: 0, lines: 0, bytes: 0 };
+  }
+
+  // 1. 字符数：统计总字符数量
+  const characters = text.length;
+
+  // 2. 单词数：使用 Intl.Segmenter 识别单词边界
+  // 这能很好地处理中英文混合文本。中文会按词组切分，英文按单词切分。
+  let words = 0;
+  try {
+    const segmenter = new Intl.Segmenter(undefined, { granularity: 'word' });
+    const segments = segmenter.segment(text);
+    for (const segment of segments) {
+      // isWordLike 为 true 表示该片段是“类词”的（非空格、非标点）
+      if (segment.isWordLike) {
+        words++;
+      }
+    }
+  } catch {
+    // 降级方案：如果不支持 Intl.Segmenter，使用正则匹配英文单词
+    // 但对中文支持较差
+    const englishWords = text.match(/\b\w+\b/g) || [];
+    const chineseChars = text.match(/[\u4e00-\u9fa5]/g) || [];
+    words = englishWords.length + chineseChars.length;
+  }
+
+  // 3. 行数：统计换行符数量
+  // 空字符串已在上方处理。非空文本至少有一行。
+  const lines = text.split('\n').length;
+
+  // 4. 字节大小：计算文本内容的字节数 (UTF-8)
+  const bytes = new TextEncoder().encode(text).length;
+
+  return { characters, words, lines, bytes };
+}
+
+/**
+ * 格式化字节大小显示（兼容旧接口，内部委托给 formatBytes）
+ *
+ * @param bytes 字节数
+ * @returns 格式化后的字符串
+ */
+export function formatByteSize(bytes: number): string {
+  return formatBytes(bytes);
+}