Add SchemeOptions (36B), WeaponSettings (4B), and ExtendedOptions (110B)
structs with from_bytes/to_bytes for safe typed access to .wsc payload
fields. Include V3 ROM defaults, scheme weapon order table, and 8 new
tests covering typed field access, roundtrips, and version boundaries.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>