fix: 清洗远程文件消息段文件名

[liuwanwan1]

变更内容

• 为 File 消息段远程下载增加文件名清洗，仅保留 basename 并移除空字节
• 下载前主动创建 AstrBot 临时目录，避免目录不存在导致写入失败
• 补充单元测试，覆盖包含路径分隔符和空字节的远程文件名

关联 Issue

Closes #8317

验证

• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run pytest tests/unit/test_file_message_component.py
• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run ruff format .
• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run ruff check .

Summary by Sourcery

Sanitize remote file names in File message downloads and ensure temporary directories exist before saving, with tests verifying the new behavior.

Bug Fixes:

• Prevent unsafe or malformed remote file names from being used directly when downloading File message components by normalizing and sanitizing the basename.
• Avoid download failures caused by missing AstrBot temporary directories by creating the directory tree before writing files.

Tests:

• Add async unit test covering File component downloads with remote names containing path separators and null bytes to verify sanitization and temp directory handling.

[sourcery-ai]

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[gemini-code-assist]

Code Review

This pull request introduces a filename sanitization function for file components and refactors the file download logic to utilize pathlib for better path management. It also includes a new unit test to verify that remote filenames are correctly sanitized. The reviewer suggested extending the sanitization logic to handle characters that are invalid on Windows filesystems (such as ':', '*', and '?') to ensure cross-platform compatibility.

[gemini-code-assist]

The _sanitize_file_component_name function correctly handles path traversal by extracting the basename and removing null bytes. However, it does not account for other characters that are invalid in filenames on certain operating systems, particularly Windows (e.g., :, *, ?, ", <, >, |). If a remote filename contains these characters, the subsequent download_file call will fail with an OSError on Windows. Consider replacing these characters with an underscore or removing them to ensure cross-platform compatibility. Additionally, as this is new functionality for handling file components, please ensure it is accompanied by unit tests.

Suggested change

	def _sanitize_file_component_name(name: str | None) -> str:
	if not name:
	return "file"
	normalized = str(name).replace("\\", "/")
	basename = PurePosixPath(normalized).name.replace("\x00", "").strip()
	if basename in {"", ".", ".."}:
	return "file"
	return basename
	def _sanitize_file_component_name(name: str | None) -> str:
	if not name:
	return "file"
	normalized = str(name).replace("\\", "/")
	basename = PurePosixPath(normalized).name.replace("\\x00", "").strip()
	# Remove or replace characters that are invalid on Windows filesystems
	for char in ':*?"<>|':
	basename = basename.replace(char, "_")
	if basename in {"", ".", ".."}:
	return "file"
	return basename

References

1. New functionality, such as handling attachments, should be accompanied by corresponding unit tests.

[liuwanwan1]

已根据 Gemini Code Assist 的建议补充处理：

• 将 Windows 文件系统非法字符 :*?"<>| 替换为 _
• 扩展单元测试覆盖这些字符和空字节/路径分隔符组合

本地验证：

• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run pytest tests/unit/test_file_message_component.py
• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run ruff format .
• UV_CACHE_DIR=/tmp/uv-cache UV_PYTHON_INSTALL_DIR=/tmp/uv-python uv run ruff check .