nx_catn_kat_gate.nx

nx_catn_kat_gate.nx -- THE NUMBER FORMATTER RENDERS NEGATIVES. PROVEN, NOT EDITED-AND-ASSUMED. ta_catn had `while m > 0` with no negative branch, so a negative emitted ZERO CHARACTERS and the MCP transport produced malformed JSON: `"exit_code":,"bytes":0`. A timed-out exec returns a negative rc, so the one value it could not print was the one that appears only when something has already gone wrong -- and the caller could not tell "timed out" from "dead tool". This KAT calls the REAL ta_catn from nx_tools_api.nx (a lib, no main, so it is importable) and pins its output. It proves the SOURCE is correct independently of whether the daemon carrying it has been deployed -- two different claims that were being conflated. ★ THE DECISIVE TOOTH IS THE LENGTH ONE: the defect produced exactly ZERO bytes, so asserting that -1 renders as TWO characters is the direct regression assertion. A tooth that only checked the digits would pass on an empty buffer left over from a previous test. license_tier: ORIGINAL expect_exit: 0