Route every VirtualFollowList DOM and Virtua position write through one reason-labelled writeScroll chokepoint that owns programmatic marking, with no change to targets, scheduling, cancellation or recorded offsets. Add an opt-in persisted logger namespace (scroll) tracing writes, follow-mode transitions and unowned movements with no layout reads when disabled; expose data-follow-mode; label the remaining external writers with the closed reason type. Releases and no-op writes keep attribution accurate. Diagnosis: the escaped-reader and hold displacements are Virtua default-size re-estimation, browser clamping and compensation, fixed in #974. Gatekeeper rounds 1-3 resolved to zero findings.
