Generate C3 NIF entry point code.

This module generates the C3 code needed to register NIFs with the Erlang runtime:

• ErlNifFunc array with function metadata
• nif_init function that returns the ErlNifEntry

Generated Code Structure

// === AUTO-GENERATED NIF ENTRY ===
ErlNifFunc[N] __c3nif_funcs__ = {
    { .name = "func1", .arity = 1, .fptr = &func1, .flags = 0 },
    { .name = "func2", .arity = 2, .fptr = &func2, .flags = erl_nif::ERL_NIF_DIRTY_JOB_CPU_BOUND },
};

ErlNifEntry __c3nif_entry__;

fn ErlNifEntry* nif_init() @export("nif_init") {
    __c3nif_entry__ = c3nif::make_nif_entry(
        "Elixir.MyModule",
        &__c3nif_funcs__,
        N,
        &on_load,  // or null
        null
    );
    return &__c3nif_entry__;
}