nx_calibrate_test.nx

nx_calibrate_test.nx -- smoke for nx_calibrate SA-2 MVP. Exercises: - canary tamper-detect (pre + post bracketing) - calibration completes without canary tamper - every microbench produces a positive measurement - cache hierarchy WITNESSED: l1 <= l2 <= ram (with tolerance band because qemu emulation may compress the hierarchy) - memory bandwidth > 0 - syscall costs > 0 (could be very small on qemu user-mode) - tier inference returns a valid sealed-enum value - sealed-enum validity gate - STRUCTURAL REPRODUCIBILITY: re-run produces same SHAPE (all fields populated, none NaN/negative, hierarchy still monotone) -- byte-equal across runs deferred to SA-7 when byzantine N-of-M reconciliation lands SA-2 verification gate per NISHI_SELF_ASSEMBLY_ROADMAP.md §8.