audit-trail-retention-decay-a-pattern-s-active-at-n-peer-sites-count-is-high-s-230f2905

THEN Implement class-dependent half-life decay (ephemeral, normal, eternal) with default half-lives and stale thresholds. Expose decay_class and freshness_factor fields in the API so consumers display ambient-vs-active honestly. Always show last_seen alongside peer count.

HALF_LIFE_DAYS = {"ephemeral": 90, "normal": 365, "eternal": 730}
STALE_THRESHOLD = {"ephemeral": 180, "normal": 365, "eternal": 540}