fix: align stats/base/dists/gumbel/quantile validation prologue with namespace convention

Reorder NaN checks in the validation prologue so the first declared
parameter (`p`) is checked first, matching the convention used by
13/14 (93%) sibling packages in `stats/base/dists/gumbel/`. Behavior
is unchanged: every branch still returns NaN.

Author: claude

lib/node_modules/@stdlib/stats/base/dists/gumbel/quantile/lib/main.js

@@ -73,9 +73,9 @@ var ln = require( '@stdlib/math/base/special/ln' );
 */
 function quantile( p, mu, beta ) {
 	if (
+		isnan( p ) ||
 		isnan( mu ) ||
 		isnan( beta ) ||
-		isnan( p ) ||
 		beta <= 0.0 ||
 		p < 0.0 ||
 		p > 1.0