relay-eval: exclude event-count outliers from coverage union
when a relay reports >1.3x the median event count (likely replaying
after a restart), exclude it from the effective union used to compute
coverage percentages. prevents a single replaying relay from dragging
all other relays' coverage scores down.
applies to both the dashboard snapshot view and the OG SVG image.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>