Constant MAX_RING_EVENTS 

const MAX_RING_EVENTS: usize = 4096;

Cap on in-memory ring size. 4096 events is comfortable for realistic resync windows (~minutes of activity at typical reducer event rates: 10–50 events per user action). Tunable upward if forensics in long sessions show truncation; downward would only be useful if we measured noticeable memory pressure from this (we don’t — Event is small and there are 4096 of them).