uv

ebca3197 - Add dedicated error message for direct filesystem paths in requirements (#2369)

Add dedicated error message for direct filesystem paths in requirements (#2369) ## Summary This is analogous to #669, but for cases in which the package name is a filesystem path. In such cases, we'll fail when parsing the _package name_, since it doesn't start with a valid character, as opposed to failing when we go to parse the remaining version specifier. Inspired by https://github.com/astral-sh/uv/issues/2356.