generic_types_test.nx

generic_types_test.nx -- exercises the monomorphization port. Declares a generic struct and uses it with two distinct type arguments in the same module. If monomorphization is working, the two instantiations produce separate Type objects keyed under mangled names (Pair$i64 and Pair$p). If broken, they collapse into one shared struct and the payloads would type- confuse. Today this file is compiled ONLY through nxc2.exe (the C-based compiler using parse.c). That establishes the reference behaviour. When nxc.nx (using parse.nx's ported monomorphization) is bootstrapped through QEMU, compiling this file with it should produce byte-identical output to the nxc2.exe version -- which will confirm parse.nx's instantiate_generic_n logic matches parse.c's for real. For now, the file serves as: 1. A live test-case for parse.c + code-gen of the feature 2. A future regression guard when parse.nx becomes the actual compiler frontend 3. Concrete documentation of what generic struct usage looks like in NishiLang