Add optimality note: exhaustive enumeration confirms magnitude 4 is minimum

README.md

@@ -71,6 +71,10 @@ But threshold logic computes OR directly - no inversion needed.
 | Bias | -1 |
 | **Total** | **4 parameters** |
 
+## Optimality
+
+Exhaustive enumeration of all 321 weight configurations at magnitudes 0-4 confirms this circuit is **already at minimum magnitude (4)**. There is exactly one valid configuration at magnitude 4, and no valid configurations exist below it.
+
 ## Usage
 
 ```python