nx_fnclosure_probe.nx

nx_fnclosure_probe.nx -- seq1337 isolation, probe 3 (DECISIVE). Probes 1+2 proved `fn` and `en` compile fine in a BARE file, disproving my filed root-cause. Remaining hypothesis: the identifiers collide with something in THAT GATE'S import closure. This reproduces the exact conditions: same two imports, same identifiers, same pc_frame call. BUILDS => identifiers are innocent and the hang was environmental (stale/torn source page, seq124). HANGS => the collision is real and closure-dependent. license_tier: ORIGINAL expect_exit: 0 No hw writes (Rule 26).