pub fn sleep_until(deadline_us: u64)Expand description
Block the calling preemptive task until the absolute time deadline_us
(plan.md §5.6 / Phase 11). sleep_ms is sleep_until(now + ms*1000);
crate::deadlines::wait_period uses this directly with a
drift-corrected deadline so periodic jitter doesn’t accumulate. No-op
outside a preemptive task context. If deadline_us has already
passed, still yields once (bounded, not a busy spin) rather than
returning immediately.