end2end_test.nx

end2end_test.nx -- prove lex.nx + parse.nx + ir.nx work together. Takes a NishiLang source string in memory, runs it through the full NishiLang-side front-end (lex → parse → IR), and verifies structural invariants on the resulting Module. This is the "nx compiles nx" demo: zero C-side compiler code touches the IR build; every byte from source to SSA goes through NishiLang-shipped modules.