Add `.exe` suffix to tool command execution on Windows

[zanieb]

Should close https://github.com/astral-sh/uv/issues/6682

[zanieb]

~Needs validation on Windows and more explicit test coverage.~

@konstin tested this and I added a test with coverage

[samypr100]

This wouldn't solve gimme-aws-creds's case right? As there's no exe's in scripts declaration.

[zanieb]

I presume not yeah.