Use dir .. for shell detection on Windows instead of uname -s

[GilgameshxZero]

Addresses the issue raised in #164 by updating how shell detection is performed on Windows.

dir has demonstrable differences between its invocations in powershell, cmd, and (git) bash, except on an empty directory. .. is likely non-empty, except in weird permissions/home directory scenarios.

Another edge case which remains untested is that of different locales. I tried setting both system and user locales to es-MX but could not get a response in powershell/cmd that was not in English.

Below are samples of dir .. on powershell, cmd, and bash.

powershell:

    Directory: C:\Users


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        11/19/2025   5:12 PM                0
d-r---         1/18/2025   5:11 PM                Public

cmd:

 Volume in drive C has no label.
 Volume Serial Number is ECAB-EE57

 Directory of C:\Users

02/16/2025  08:05 PM    <DIR>          .
11/19/2025  05:12 PM    <DIR>          0
01/18/2025  05:11 PM    <DIR>          Public
               0 File(s)              0 bytes
               3 Dir(s)  908,322,545,664 bytes free

bash:

0  All\ Users  Default  Default\ User  desktop.ini  Public