fix: order validation checks by parameter position in stats/base/dists/cauchy/pdf

Reorder NaN guards so checks follow declaration order `(x, x0, gamma)`.
Behavior unchanged: any matching branch returns `NaN`.

Author: claude

lib/node_modules/@stdlib/stats/base/dists/cauchy/pdf/lib/main.js

@@ -68,8 +68,8 @@ function pdf( x, x0, gamma ) {
 	var denom;
 	if (
 		isnan( x ) ||
-		isnan( gamma ) ||
 		isnan( x0 ) ||
+		isnan( gamma ) ||
 		gamma <= 0.0
 	) {
 		return NaN;