fix: 修复 CI Python 3.13 测试失败问题

- 移除 TxtReader 中无效的 'ansi' 编码（Python 不支持）
- 修复路径遍历测试使用 .txt 扩展名以通过类型检查

Author: xt765

mcp_documents_reader.py

@@ -115,7 +115,7 @@ class TxtReader(DocumentReader):
     def read(self, file_path: str) -> str:
         """Read and extract text from TXT file with encoding handling"""
         # Supported encodings in priority order
-        encodings = ["utf-8", "gbk", "gb2312", "ansi", "latin-1"]
+        encodings = ["utf-8", "gbk", "gb2312", "latin-1"]
 
         for encoding in encodings:
             try:

tests/test_tools.py

@@ -189,8 +189,8 @@ def test_read_document_with_path_traversal(
         Args:
             mock_context_with_temp_dir: 带有临时目录的模拟上下文
         """
-        # 尝试路径遍历攻击
-        result = read_document(mock_context_with_temp_dir, "../../../etc/passwd")
+        # 尝试路径遍历攻击（使用 .txt 扩展名以通过类型检查）
+        result = read_document(mock_context_with_temp_dir, "../../../etc/passwd.txt")
 
         # 应返回文件不存在的错误
         assert "Error:" in result