nx_time.nx

nx_time.nx -- monotonic wall-clock time + duration utilities. nx_clock_now_ns() -- monotonic nanoseconds via the clock_gettime(CLOCK_MONOTONIC) syscall (113 on RV64 Linux). This is what nx_trace wires to once spans get real timestamps. Per the decade-horizon doctrine, we do NOT trust gettimeofday() or wall-clock realtime here -- those skew, leap, and re-set, and any logic that mixes them with monotonic produces phantom bugs at boundaries. For LOGICAL ordering use nx_trace's tick counter; for PROFILING use nx_clock_now_ns(). Don't cross-mix in the same measurement. Design references: Linux clock_gettime(2) -- monotonic clock contract Go runtime nanotime() -- platform-portable monotonic clock Java System.nanoTime -- JVM monotonic clock guarantee Rust std::time::Instant -- monotonic-only Duration source