Plugin: use pluginClass.name for reliable class name extraction

plugin.register() now uses pluginClass.name before falling back to
the toString() regex. Fixes class name extraction when bundlers
(e.g. esbuild) strip class names from minified output, which caused
"plugin extends already registered" errors when registering multiple plugins.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: obiot

packages/melonjs/src/plugin/plugin.ts

@@ -95,7 +95,8 @@ export function register(
 	...args: any[]
 ): void {
 	// derive name from class if not provided
-	const pluginName = name || pluginClass.toString().match(/ (\w+)/)![1];
+	const pluginName =
+		name || pluginClass.name || pluginClass.toString().match(/ (\w+)/)![1];
 
 	// ensure me.plugins[name] is not already "used"
 	if (cache[pluginName]) {