fix(worker): use winner identity for Glicko-2 pairwise scoring

Raw game scores (capture points) are tied in most matches since the
winner is determined by an energy/bots-alive tiebreaker. This caused
Glicko-2 delta=0, leaving rating_mu frozen at 1500 for all bots.

Now winner gets 1.0, non-winners 0.0, draws 0.5 — correct pairwise
win/loss signal for Glicko-2 convergence.

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

cmd/acb-worker/main.go

@@ -452,8 +452,16 @@ func (w *Worker) computeRatingUpdates(claimData *JobClaimData, result *MatchResu
 			Phi:   p.RatingPhiBefore,
 			Sigma: p.RatingSigmaBefore,
 		}
-		// Normalize scores for Glicko-2 (higher is better)
-		scores[i] = float64(result.Scores[p.BotID])
+		// Use winner identity for pairwise Glicko-2 scoring.
+		// Raw game scores (captures) are often tied, so we use the declared
+		// winner as the discriminator: winner=1.0, others=0.0, draw=0.5.
+		if result.WinnerID == "" {
+			scores[i] = 0.5
+		} else if result.WinnerID == p.BotID {
+			scores[i] = 1.0
+		} else {
+			scores[i] = 0.0
+		}
 	}
 
 	// Compute rating updates