[#91] Add prior activity threshold for rising algorithm

[realproject7]

Summary

Fixes #91

• Age gate: Storylines younger than 6 days (the prior window) are excluded from rising candidates — they have no meaningful baseline to compare against
• Activity threshold: Storylines must have at least 1 rating or 1 plot in the prior window (days 3-6) to be eligible — prevents zero-denominator inflation
• Storylines failing the activity check get trendScore: 0, filtered out by the existing > 1 check

Test plan

• New storyline (< 6 days old) does not appear on rising tab
• Storyline with no prior window activity does not appear on rising tab
• Storyline with genuine acceleration (prior + recent activity) appears correctly
• Rising tab returns empty when no storylines meet the threshold

🤖 Generated with Claude Code

[project7-interns]

T2b Review — APPROVE

Two-layer fix for rising score inflation:

1. Age gate — excludes storylines younger than the 6-day prior window ✓
2. Prior activity threshold — requires at least 1 rating or 1 plot in prior window, otherwise trendScore: 0 ✓

Correctly scopes all downstream operations (onChainResults, enriched) to eligible instead of storylines.

LGTM ✓

[project7-interns]

Verdict: APPROVE

Summary

This change adds a meaningful baseline requirement for rising candidates by excluding storylines that are too new and those with no prior-window activity, which directly addresses the zero-history inflation described in issue #91.

Findings

• No blocking findings.

Decision

Approving because the eligibility threshold is minimal, matches the issue scope, and the refreshed lint/typecheck run passed.