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/deprecated/src/index.js

@@ -0,0 +1,82 @@
+/**
+ * WordPress dependencies
+ */
+import { doAction } from '@wordpress/hooks';
+
+/**
+ * Object map tracking messages which have been logged, for use in ensuring a
+ * message is only logged once.
+ *
+ * @type {Record<string, true | undefined>}
+ */
+export const logged = Object.create( null );
+
+/**
+ * Logs a message to notify developers about a deprecated feature.
+ *
+ * @param {string} feature               Name of the deprecated feature.
+ * @param {Object} [options]             Personalisation options
+ * @param {string} [options.since]       Version in which the feature was deprecated.
+ * @param {string} [options.version]     Version in which the feature will be removed.
+ * @param {string} [options.alternative] Feature to use instead
+ * @param {string} [options.plugin]      Plugin name if it's a plugin feature
+ * @param {string} [options.link]        Link to documentation
+ * @param {string} [options.hint]        Additional message to help transition away from the deprecated feature.
+ *
+ * @example
+ * ```js
+ * import deprecated from '@wordpress/deprecated';
+ *
+ * deprecated( 'Eating meat', {
+ * 	since: '2019.01.01'
+ * 	version: '2020.01.01',
+ * 	alternative: 'vegetables',
+ * 	plugin: 'the earth',
+ * 	hint: 'You may find it beneficial to transition gradually.',
+ * } );
+ *
+ * // Logs: 'Eating meat is deprecated since version 2019.01.01 and will be removed from the earth in version 2020.01.01. Please use vegetables instead. Note: You may find it beneficial to transition gradually.'
+ * ```
+ */
+export default function deprecated( feature, options = {} ) {
+	const { since, version, alternative, plugin, link, hint } = options;
+
+	const pluginMessage = plugin ? ` from ${ plugin }` : '';
+	const sinceMessage = since ? ` since version ${ since }` : '';
+	const versionMessage = version
+		? ` and will be removed${ pluginMessage } in version ${ version }`
+		: '';
+	const useInsteadMessage = alternative
+		? ` Please use ${ alternative } instead.`
+		: '';
+	const linkMessage = link ? ` See: ${ link }` : '';
+	const hintMessage = hint ? ` Note: ${ hint }` : '';
+	const message = `${ feature } is deprecated${ sinceMessage }${ versionMessage }.${ useInsteadMessage }${ linkMessage }${ hintMessage }`;
+
+	// Skip if already logged.
+	if ( message in logged ) {
+		return;
+	}
+
+	/**
+	 * Fires whenever a deprecated feature is encountered
+	 *
+	 * @param {string}  feature             Name of the deprecated feature.
+	 * @param {?Object} options             Personalisation options
+	 * @param {string}  options.since       Version in which the feature was deprecated.
+	 * @param {?string} options.version     Version in which the feature will be removed.
+	 * @param {?string} options.alternative Feature to use instead
+	 * @param {?string} options.plugin      Plugin name if it's a plugin feature
+	 * @param {?string} options.link        Link to documentation
+	 * @param {?string} options.hint        Additional message to help transition away from the deprecated feature.
+	 * @param {?string} message             Message sent to console.warn
+	 */
+	doAction( 'deprecated', feature, options, message );
+
+	// eslint-disable-next-line no-console
+	console.warn( message );
+
+	logged[ message ] = true;
+}
+
+/** @typedef {import('utility-types').NonUndefined<Parameters<typeof deprecated>[1]>} DeprecatedOptions */

node_modules/@wordpress/deprecated/src/test/index.js

@@ -0,0 +1,106 @@
+/**
+ * WordPress dependencies
+ */
+import { didAction } from '@wordpress/hooks';
+
+/**
+ * Internal dependencies
+ */
+import deprecated, { logged } from '../';
+
+describe( 'deprecated', () => {
+	afterEach( () => {
+		for ( const key in logged ) {
+			delete logged[ key ];
+		}
+	} );
+
+	it( 'should show a deprecation warning', () => {
+		deprecated( 'Eating meat' );
+
+		expect( console ).toHaveWarnedWith( 'Eating meat is deprecated.' );
+	} );
+
+	it( 'should show a deprecation warning with a since', () => {
+		deprecated( 'Eating meat', { since: '2019.01.01' } );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated since version 2019.01.01.'
+		);
+	} );
+
+	it( 'should show a deprecation warning with a version', () => {
+		deprecated( 'Eating meat', { version: '2020.01.01' } );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated and will be removed in version 2020.01.01.'
+		);
+	} );
+
+	it( 'should show a deprecation warning with an alternative', () => {
+		deprecated( 'Eating meat', {
+			since: '2019.01.01',
+			version: '2020.01.01',
+			alternative: 'vegetables',
+		} );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated since version 2019.01.01 and will be removed in version 2020.01.01. Please use vegetables instead.'
+		);
+	} );
+
+	it( 'should show a deprecation warning with an alternative specific to a plugin', () => {
+		deprecated( 'Eating meat', {
+			version: '2020.01.01',
+			alternative: 'vegetables',
+			plugin: 'the earth',
+		} );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated and will be removed from the earth in version 2020.01.01. Please use vegetables instead.'
+		);
+	} );
+
+	it( 'should show a deprecation warning with a link', () => {
+		deprecated( 'Eating meat', {
+			version: '2020.01.01',
+			alternative: 'vegetables',
+			plugin: 'the earth',
+			link: 'https://en.wikipedia.org/wiki/Vegetarianism',
+		} );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated and will be removed from the earth in version 2020.01.01. Please use vegetables instead. See: https://en.wikipedia.org/wiki/Vegetarianism'
+		);
+	} );
+
+	it( 'should show a deprecation warning with a hint', () => {
+		deprecated( 'Eating meat', {
+			since: '2019.01.01',
+			version: '2020.01.01',
+			alternative: 'vegetables',
+			plugin: 'the earth',
+			hint: 'You may find it beneficial to transition gradually.',
+		} );
+
+		expect( console ).toHaveWarnedWith(
+			'Eating meat is deprecated since version 2019.01.01 and will be removed from the earth in version 2020.01.01. Please use vegetables instead. Note: You may find it beneficial to transition gradually.'
+		);
+	} );
+
+	it( 'should show a message once', () => {
+		deprecated( 'Eating meat' );
+		deprecated( 'Eating meat' );
+
+		expect( console ).toHaveWarned();
+		// eslint-disable-next-line no-console
+		expect( console.warn ).toHaveBeenCalledTimes( 1 );
+	} );
+
+	it( 'should do an action', () => {
+		deprecated( 'turkey', { alternative: 'tofurky' } );
+
+		expect( console ).toHaveWarned();
+		expect( didAction( 'deprecated' ) ).toBeTruthy();
+	} );
+} );