fix: prevent asset conflicts between React and Grid.js versions

Add coexistence checks to all enqueue methods to prevent loading
both React and Grid.js assets simultaneously.

Changes:
- ReactAdmin.php: Only enqueue React assets when ?react=1
- Init.php: Skip Grid.js when React active on admin pages
- Form.php, Coupon.php, Access.php: Restore classic assets when ?react=0
- Customer.php, Product.php, License.php: Add coexistence checks

Now the toggle between Classic and React versions works correctly.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

node_modules/@wordpress/components/build-module/h-stack/component.js

@@ -0,0 +1,41 @@
+import { createElement } from "react";
+/**
+ * Internal dependencies
+ */
+
+import { contextConnect } from '../context';
+import { View } from '../view';
+import { useHStack } from './hook';
+function UnconnectedHStack(props, forwardedRef) {
+  const hStackProps = useHStack(props);
+  return createElement(View, {
+    ...hStackProps,
+    ref: forwardedRef
+  });
+}
+
+/**
+ * `HStack` (Horizontal Stack) arranges child elements in a horizontal line.
+ *
+ * `HStack` can render anything inside.
+ *
+ * ```jsx
+ * import {
+ * 	__experimentalHStack as HStack,
+ * 	__experimentalText as Text,
+ * } from `@wordpress/components`;
+ *
+ * function Example() {
+ * 	return (
+ * 		<HStack>
+ * 			<Text>Code</Text>
+ * 			<Text>is</Text>
+ * 			<Text>Poetry</Text>
+ * 		</HStack>
+ * 	);
+ * }
+ * ```
+ */
+export const HStack = contextConnect(UnconnectedHStack, 'HStack');
+export default HStack;
+//# sourceMappingURL=component.js.map