Add xbox 360 platform

[mkst]

Xbox 360 decomp projects:

• Dance Central 3

Available Compilers:

• MSVC (16.00.11886.00) from https://files.decomp.dev/compilers_20250725.zip

Difficulties:

• No assembler/objdumper for eXtended COFF (PPC) format that cl.exe produces:
  • No support for creating scratches via assembly (only uploading .obj)
  • No support for asm-differ (only objdiff) - breaks scoring etc.
• cl.exe does not run via wibo (runs fine under wine)

If we are to add Xbox 360 as a platform to the site I suggest we have a way to prevent users trying to upload asm (until/unless an assembler is found or written) as they will just get confused/annoyed.

Changes required:

• add new xbox360 platform (easy)
• add new compiler (easy)
• add b"\xf2\x01" to COFF list (easy)
• objdiff scoring (medium)
• graceful fallback for lack of as/objdump (i.e. zero asm-differ support)
• disablexbox360 platform in /new scratch patch