feat(ga): generation summary stats (median/max/p90/entropy)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/multi_swarm/ga/summary.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import math
+
+import numpy as np
+
+
+def generation_summary(fitnesses: list[float], n_bins: int = 10) -> dict[str, float]:
+    arr = np.asarray(fitnesses, dtype=float)
+    if arr.size == 0:
+        return {"median": 0.0, "max": 0.0, "p90": 0.0, "entropy": 0.0}
+    median = float(np.median(arr))
+    fmax = float(np.max(arr))
+    p90 = float(np.percentile(arr, 90))
+
+    if fmax > 0:
+        normalized = arr / fmax
+    else:
+        normalized = arr
+
+    hist, _ = np.histogram(normalized, bins=n_bins, range=(0.0, 1.0))
+    total = hist.sum()
+    probs = hist / total if total > 0 else hist
+    entropy = float(-sum(p * math.log(p) for p in probs if p > 0))
+
+    return {"median": median, "max": fmax, "p90": p90, "entropy": entropy}