Add support for .pth files

> A path configuration file is a file whose name has the form **name.pth** and exists in one of the four directories mentioned above; its contents are additional items (one per line) to be added to sys.path. Non-existing items are never added to sys.path, and no check is made that the item refers to a directory rather than a file. No item is added to sys.path more than once. Blank lines and lines beginning with # are skipped. Lines starting with import (followed by space or tab) are executed.

https://docs.python.org/3/library/site.html

.pth files are often used by python packaging systems (like uv, etc...) to make working on the current project more elegant, by pointing from the .venv/ path to the project path.

从链接的 Python site 文档以及 componentize-py 对 .venv/ 路径的处理开始。将所需行为与 .pth 关于路径条目、注释、空行、重复条目、缺失路径和 import 行的规则进行比较。完成的标准是，受支持的 .pth 文件能够将有效的项目路径添加到 sys.path，同时不添加无效或重复的条目。

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