Function is_dig_opcode 

pub const fn is_dig_opcode(opcode: u8) -> bool

Whether opcode belongs to the DIG band rather than Chia’s namespace.

This is a band test, not an assigned test: an unassigned value such as 250 is still DIG’s to allocate, and a link must route it to DIG handling (where it is rejected as unknown) rather than to a Chia decoder that would reject the whole connection.