Switch FAT partition to read-only and make look like a CD

Do we really need people to edit uEnv.txt from the shared drive these days? Perhaps, but if Linux is booted it is rare that you can't at least open the virtual serial console and edit from the Linux side. I'm concerned about people corrupting it and it would allow autorun.inf to work such that Windows users start to discover the START.htm.

Start by reviewing how the FAT partition is currently exposed and how uEnv.txt is edited through the shared drive or virtual serial console. Check the expected Windows behavior for autorun.inf and START.htm, then clarify the desired read-only and CD-like behavior before implementation.

Written by the indexing model from the issue text.