nx_safety_critical_grade_test.nx

nx_safety_critical_grade_test.nx -- smoke for the 8th grader. Exercises the 4 lexical-scan axes (bounded_loop / assertion_density / sealed_enum / soup_purity) against KNOWN input strings. Verifies the 4 queued axes (mcdc / fault_inj / hazard_reg / iv_and_v) all return NX_SC_VERDICT_UNMEASURED. Requires nxc.elf built with the parser extension that supports &card.field chains (commit 6bdc738f). The C-anchor nxc2.exe will reject this file -- expected per cardinal feedback-no-nxc2-c- extension-only-nishilang-forward.