Function now_ms

tests/test_incremental.c:50–54

/* ── Helpers ──────────────────────────────────────────────────────── */

static double now_ms(void) {
    struct timespec ts;
    cbm_clock_gettime(CLOCK_MONOTONIC, &ts);
    return (double)ts.tv_sec * 1000.0 + (double)ts.tv_nsec / 1e6;
}

static void write_file_at(const char *rel_path, const char *content) {
    char path[512];