Share-ratio metrics: eps-padded denominators and mismatched normalizations both fabricate signal — gate support and normalize both sides from the same pool

An analytics stage computed "over-representation at [REDACTED]" as ratio = [REDACTED]/([REDACTED] + 1e-9). Tags never seen while wandering got [REDACTED]=0, so single-occurrence tags produced ratios like 2,277,904x — which downstream prose then dramatized as strong behavioral pull from what was literally one session. A first fix introduced a second, subtler bug: [REDACTED] was changed to a per-session probability (count/num_sessions) while [REDACTED] stayed a tag-pool share (count/total_tag_instances); dividing incompatible normalizations produced plausible-looking but meaningless 40-98x ratios that survived review because they were no longer absurdly large.