cap terminal reward scale (bounded score bonus) and restore single-battle campaigns

computeRoundReward used cumulative totalScore/50 — unbounded in long battles
(vLoss 353 at round 3160 → 25745 by 3871 in the 5841-round attempt). Cap the
score term at 400 before /50: bonus ∈ [0,8], so the critic's value scale stays
stable regardless of battle length and across battle boundaries.

Reverts the 60-round battle chunking (186e005/da2f825): one battle per
campaign for the whole remaining budget; keeps the crash-restart loop, the
mid-battle freeze guard and the end-of-battle counter completeness check.

Cert (5211, single 60-round battle): 59/60 wins (sole loss = cold-start round
1, score 61), vLoss avg 36.1 / max 148.5, gNorm max 596, zero NaN, zero
restarts, counter check passed. Weights persist to round 5211.

PPO_Bot/training.nim

@@ -69,7 +69,9 @@ proc computeTickReward*(myEnergyDelta, enemyEnergyDelta: float32;
 
 proc computeRoundReward*(roundScore: float32): float32 =
   ## Normalise round-end score to a rough ±6 range (doubled win signal).
-  result = roundScore / 50.0'f32
+  ## ponytail: cap cumulative score at 400 before /50 — bounded terminal bonus
+  ## keeps critic value scale stable across battle boundaries and long battles.
+  result = min(roundScore, 400.0'f32) / 50.0'f32
 
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