feat: 支持 Python 3.8+ (0.3.0)

- requires-python >=3.8, classifiers 增加 3.8/3.9
- 代码经 ast feature_version=(3,8) 校验, 无 3.9+ 专属语法; str|None 等注解由 future annotations 延迟求值
- CI 测试/构建/smoke 矩阵扩展为 3.8-3.14, 裸资产数 6→8
- 注意: Windows runner 需预装 Python 3.8 与 3.9 (py launcher)

pyproject.toml

@@ -7,11 +7,13 @@ name = "dlp-io"
 dynamic = ["version"]
 description = "io-compatible file reads through an approved Python helper on Windows DLP hosts"
 readme = "docs/DLP_IO_LIBRARY.md"
-requires-python = ">=3.10"
+requires-python = ">=3.8"
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Operating System :: Microsoft :: Windows",
     "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",