nx_gguf_meta_test.nx

nx_gguf_meta_test.nx -- smoke for nx_gguf_meta.nx. Builds a synthetic GGUF with 4 metadata entries: "n_layers" U32 -> 32 "rope_base" F32 -> 10000.0 "arch" STRING -> "llama" "vocab" ARRAY of U32 with 3 elements -> [100, 200, 300] Verifies: - find returns OK with correct value_off + type for each - typed readers produce expected values - missing key returns NOT_FOUND - array helpers expose inner_type + count + first_elt_off - array element walk via array_advance produces correct values