v0.6.5: scheduling-mode-aware + jitter-aware reorder-window auto-tuning The real next lever in the throughput investigation. auto_tune_reorder_window computed its suggestion from RTT spread across every Up link regardless of whether the active scheduling mode could deliver from more than one -- with primary_link_mode/follow_peer_primary settled on a single link, an idle backup's own RTT was still inflating the window and adding real, unnecessary latency. Now gated on Scheduler::primary(): settled single link uses only that link's own jitter (multiplier 4.0, mirroring TCP's Jacobson/Karels RTO = SRTT + 4*RTTVAR); no settled primary combines the existing RTT-spread term with a new worst-case-jitter term. Targets the sawtooth TCP retransmission-timeout cycling observed in production despite 0% probe-reported loss and an 886 Mbps raw-path ceiling.