For each closed round1 streak with L ≥ threshold, counts draws in
the next N matches after the closing draw (N is fixed at build time
per team based on their post_window_max).
Round1 length distribution with cutoffs for p95 / p99 / tukey15 / tukey3. Cutoffs computed server-side from the team's own R1 lengths.
A chain is a sequence of consecutive round2 entries where each
successor's triggered_by equals the previous entry's
length (a round2 that reached threshold re-enters as the
next round1). Chains of length ≥ 2. Computed from canonical JSON,
so the set differs from the curated chain_analyzer_report.txt.
Alerts are computed by src/draw_magnets.py on the
competitive_only / keep variant only — independent of
the variant dropdown above.