1.6.6 started treating >=3.13t as a path #175

Nox users might write python=">=3.13t" for a session. This used to "work" (as in, it did return a range, though it actually didn't set free_threaded). Now it looks for an executable named >=3.13t.

It would be nice if a trailing t on a specifier would set free_threaded=True, and then process the specifier without the trailing t. Or maybe throw an error.

We were also testing invalid specifiers, like >=3.13., which now also look for a path, but that's really just our weird testing. Would it be reasonable to assume a python path can't contain >=< characters, at least if if doesn't have /\, and error?

Nothing has to change, we are fixing up our tests and adding the free-threading processing mentioned above, but these are some thoughts.