self_parse_test.nx

self_parse_test.nx -- feed parse.nx's OWN source through the nx-side lex + parse pipeline and verify it completes without structural crashes. This is a soft self-host milestone: parse.nx, tokenized by lex.nx and parsed by parse.nx at runtime, should produce a Module with roughly the same number of functions it actually declares. We don't bit-diff the IR yet; only check that the pipeline reaches the end without aborting. Source-text-embedding: we use a smaller but representative NishiLang program that exercises most of parse.nx's dispatch paths in a way the linker-embedded string literal can stretch to.