nx_bench_companion_timed.nx

nx_bench_companion_timed.nx -- wall-clock-wrapped substrate measurement. Sibling to [[nx_bench_companion]]. Adds REAL wall-clock timing (via nx_clock_monotonic_ns) around bench capture, so substrate counters AND elapsed microseconds land in one report. Per CARDINAL [[feedback-no-strawman-perf-comparisons]]: wall-clock under qemu-riscv64 is NOT comparable to wall-clock on physical hardware (qemu is single-threaded + interpreter-emulated). What it IS: the substrate's first real time-measurement primitive, so future physical-hardware bench runs use the same call. When the Phase E + physical-board arcs land, this primitive doesn't change; only the wall-clock number does.