test: combo snowball analysis — 60.4% rate, under 70% threshold

Simulated 1000 fights with 80% accuracy and equal speed. First-to-lead
wins 60.4% of decided fights, confirming combo system is balanced.
No decay or comeback mechanics needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/engine/scoring-analysis.test.ts

@@ -258,6 +258,59 @@ describe('scoring competitiveness analysis', () => {
     expect(true).toBe(true)
   })
 
+  it('RESEARCH: combo system snowball analysis — first-to-lead win rate', () => {
+    const N = 1000
+    let firstLeadWins = 0, nonFirstLeadWins = 0, draws = 0
+
+    for (let i = 0; i < N; i++) {
+      const result = simulateFight({
+        bothCorrect: false,
+        botAAccuracy: 0.8,
+        botBAccuracy: 0.8,
+        botASpeedMs: 1200,
+        botBSpeedMs: 1200,
+        speedVariance: 400,
+        rounds: 20,
+      })
+
+      // Determine who won the first non-draw round
+      let firstLeader: string | null = null
+      for (const r of result.rounds) {
+        if (r.winnerId) {
+          firstLeader = r.winnerId
+          break
+        }
+      }
+
+      if (!result.winnerId) {
+        draws++
+      } else if (result.winnerId === firstLeader) {
+        firstLeadWins++
+      } else {
+        nonFirstLeadWins++
+      }
+    }
+
+    const snowballRate = firstLeadWins / (firstLeadWins + nonFirstLeadWins) * 100
+
+    const section = [
+      '## Combo System Snowball Analysis (1000 fights, 80% accuracy, equal speed)',
+      '',
+      `- First-to-lead wins: ${firstLeadWins} (${snowballRate.toFixed(1)}% of decided fights)`,
+      `- Non-first-lead wins: ${nonFirstLeadWins}`,
+      `- Draws: ${draws}`,
+      `- Snowball rate: ${snowballRate.toFixed(1)}% (target: <70%)`,
+      '',
+    ]
+    reportLines.push(...section)
+
+    console.log('\n=== COMBO SNOWBALL ANALYSIS ===')
+    section.forEach(l => console.log(`  ${l}`))
+
+    // Soft assertion
+    expect(true).toBe(true)
+  })
+
   it('writes scoring analysis reports', () => {
     const __filename = fileURLToPath(import.meta.url)
     const projectRoot = resolve(dirname(__filename), '..', '..', '..')