timeout_at is pre-send anchored (F-04), so it can precede the same
probe's post-send sent_at when probe_timeout is small relative to the
send-call duration. Rolling-window eviction assumes non-decreasing
event timestamps, so clamp the internal StatsEvent::Loss windowing
value without changing the public EchoLoss.timeout_at field. Also
correct an AGENTS.md claim that sent_at feeds the downstream one-way
delay, which it does not.
Allow one-way delay samples to represent negative values caused by wall-clock skew between client and server. Update CLI output and statistics collection to correctly handle and report these signed durations.
Hide internal fields to improve type safety and provide helper methods for unit conversions and negative value checks. Fix several feature-gated test compilation issues.
Simplify RttSample by merging signed and unsigned fields into a single SignedDuration for adjusted and effective RTT. This ensures accurate reporting and statistics when server processing time exceeds raw RTT.
Nils Andreas Svee