Time, Randomness and Formatting

Three standard-library tools every trading program needs. We see why a latency measurement must use steady_clock (the system clock can be set back mid-measurement), how chrono durations carry their units in the type, why rand() % 6 is biased while an engine plus a distribution is flat and reproducible, and how std::format checks its format string at compile time and ran about twice as fast as a string stream on a Mac.