verify(bf-413): confirm all mechanics iteration work completed

Verified all 5 backlog items:
- Combat kill scoring (engine/turn.go:272-275)
- Fitness formula blending win rate + kill rate (run.go:608)
- CombatDeaths tracking through arena (arena.go:204-221)
- Behavior vector derived from actual kill rate (run.go:614-625)
- Flee thresholds with outnumber logic (farmer/gatherer/siege bots)

All mechanics now make combat economically necessary for the evolver.

notes/bf-413-verification.md

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+# Bead bf-413 Verification
+
+## Date: 2025-06-17
+
+Verified that all backlog items from the Genesis AI Code Battle Mechanics Iteration bead are complete:
+
+### Code Verification Results
+
+✅ **Combat Kill Scoring** (engine/turn.go:272-275)
+```go
+if e.Owner < len(gs.Players) {
+    gs.Players[e.Owner].Score += gs.Config.KillScore
+}
+```
+
+✅ **Fitness Formula** (cmd/acb-evolver/run.go:608)
+```go
+fitness := 0.7*winRate + 0.3*killRate
+```
+
+✅ **CombatDeaths Tracking** (cmd/acb-evolver/internal/arena/arena.go:204-221)
+- TotalKills and KillRate computed from arena outcomes
+- CombatDeaths array tracks kills per player
+
+✅ **Behavior Vector from Kill Rate** (cmd/acb-evolver/run.go:614-625)
+```go
+aggression := killRate
+if aggression > 1.0 {
+    aggression = 1.0
+}
+behaviorVec = []float64{aggression, program.BehaviorVector[1]}
+```
+
+✅ **Flee Thresholds with Outnumber Logic** 
+- bots/farmer/strategy.go:262-296
+- bots/gatherer/strategy.go:112-142
+- bots/siege/strategy.go:282-312
+
+All mechanics now make combat economically necessary:
+- Bots only flee when locally outnumbered AND enemies are in attack range
+- Kill rate contributes 30% to evolver fitness
+- Aggression is derived from actual combat performance, not LLM self-report
+
+## Status
+
+All 5 backlog items completed and verified. The evolutionary loop now has proper incentives for combat aggression.