refactor(i18n): 移除 chrome.i18n 国际化，统一使用中文硬编码

移除 chromeI18n 工具、_locales 翻译文件和 manifest default_locale 配置，
将所有 UI 文案改为直接硬编码中文，并更新相关测试与文档。

src/components/TextInputArea.tsx

@@ -1,6 +1,5 @@
 import React, { forwardRef, useCallback, useImperativeHandle, useRef, useState } from 'react';
 import { X } from 'lucide-react';
-import { useI18n } from '@/utils/chromeI18n';
 import { cn } from '@/lib/utils';
 import { toast } from 'sonner'; // 推荐使用 shadcn 的默认 Toast
 import { CopyButton } from '@/components/CopyButton';
@@ -114,8 +113,7 @@ const TextInputArea = forwardRef<HTMLTextAreaElement, TextInputAreaProps>((props
   const [internalValue, setInternalValue] = useState(defaultValue);
   const [error, setError] = useState<string>('');
 
-  const { t } = useI18n('common');
-  const placeholder = placeholderProp ?? t('textInputArea.placeholder');
+  const placeholder = placeholderProp ?? '请输入文本';
 
   const isControlled = controlledValue !== undefined;
   const value = isControlled ? controlledValue : internalValue;
@@ -159,7 +157,7 @@ const TextInputArea = forwardRef<HTMLTextAreaElement, TextInputAreaProps>((props
   const handleChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
     const newVal = e.target.value;
     if (maxLength && newVal.length > maxLength) {
-      const msg = t('charCount', { count: maxLength });
+      const msg = `内容不能超过 ${maxLength} 个字符`;
       setError(msg);
       toast.warning(msg);
       return;
@@ -181,9 +179,9 @@ const TextInputArea = forwardRef<HTMLTextAreaElement, TextInputAreaProps>((props
     onChange?.('');
     setError('');
     internalRef.current?.focus();
-    toast.success(t('textInputArea.cleared'));
+    toast.success('已清空');
     onClear?.();
-  }, [isControlled, onChange, onClear, t]);
+  }, [isControlled, onChange, onClear]);
 
   const handleAction = useCallback(
     (action: ToolbarAction) => {
@@ -272,18 +270,13 @@ const TextInputArea = forwardRef<HTMLTextAreaElement, TextInputAreaProps>((props
             {/* 右侧系统按钮组 */}
             <div className="flex items-center gap-1.5 ml-auto shrink-0">
               {allowCopy && value && (
-                <CopyButton
-                  text={value}
-                  tooltip={t('textInputArea.copyContent')}
-                  size="sm"
-                  className="h-7 w-7 p-1"
-                />
+                <CopyButton text={value} tooltip={'复制内容'} size="sm" className="h-7 w-7 p-1" />
               )}
               {showClear && value && !disabled && !readOnly && (
                 <button
                   type="button"
                   onClick={handleClear}
-                  aria-label={t('textInputArea.clear')}
+                  aria-label={'清空'}
                   className="p-1 h-7 w-7 flex items-center justify-center rounded-md text-muted-foreground hover:text-destructive hover:bg-destructive/10 transition-colors focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring"
                 >
                   <X className="h-4 w-4" />