_rc6_gate.nx

_rc6_gate.nx -- standing REGRESSION GATE for R1-T1-004 (nxasm rc=6 ctx-x-output-path class). Debt-paydown, not skip: the alleged nxasm-codegen cause was dataflow-REFUTED (Doctor: outpath store dominates its read) and is NON-REPRODUCIBLE from the standard sovereign fork+execve spawn (this gate's POS leg, incl. the exact real elfpath nx_sov_build_run mitigates away). So instead of leaving a workaround masking an unverified ghost, this gate makes the invariant CONTINUOUSLY CHECKED: POS : a SOVEREIGN parent assembles ONE real .s to N real output-path strings -> ALL must rc=0 (if the ctx-x-path class ever returns, a real path exits 6 here and the gate goes RED). NEG : the SAME .s to a genuinely-unwritable path MUST exit 6 (proves nxasm's open-failure detection + the loud diagnostic stay alive -- no-false-green; if nxasm ever decoded an open-fail as success the gate goes RED). GREEN iff (all POS rc=0) AND (NEG rc=6). Writes a machine-matchable verdict to rc6_gate.log.