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/eslint-plugin/utils/constants.js

@@ -0,0 +1,62 @@
+/**
+ * List of translation functions exposed by the `@wordpress/i18n` package.
+ *
+ * @type {Set<string>} Translation functions.
+ */
+const TRANSLATION_FUNCTIONS = new Set( [ '__', '_x', '_n', '_nx' ] );
+
+/**
+ * Regular expression matching format placeholder syntax.
+ *
+ * The pattern for matching named arguments is a naive and incomplete matcher
+ * against valid JavaScript identifier names.
+ *
+ * via Mathias Bynens:
+ *
+ * >An identifier must start with $, _, or any character in the Unicode
+ * >categories “Uppercase letter (Lu)”, “Lowercase letter (Ll)”, “Titlecase
+ * >letter (Lt)”, “Modifier letter (Lm)”, “Other letter (Lo)”, or “Letter
+ * >number (Nl)”.
+ * >
+ * >The rest of the string can contain the same characters, plus any U+200C zero
+ * >width non-joiner characters, U+200D zero width joiner characters, and
+ * >characters in the Unicode categories “Non-spacing mark (Mn)”, “Spacing
+ * >combining mark (Mc)”, “Decimal digit number (Nd)”, or “Connector
+ * >punctuation (Pc)”.
+ *
+ * If browser support is constrained to those supporting ES2015, this could be
+ * made more accurate using the `u` flag:
+ *
+ * ```
+ * /^[$_\p{L}\p{Nl}][$_\p{L}\p{Nl}\u200C\u200D\p{Mn}\p{Mc}\p{Nd}\p{Pc}]*$/u;
+ * ```
+ *
+ * @see http://www.pixelbeat.org/programming/gcc/format_specs.html
+ * @see https://mathiasbynens.be/notes/javascript-identifiers#valid-identifier-names
+ *
+ * @type {RegExp}
+ */
+const REGEXP_SPRINTF_PLACEHOLDER =
+	/%(((\d+)\$)|(\(([$_a-zA-Z][$_a-zA-Z0-9]*)\)))?[ +0#-]*\d*(\.(\d+|\*))?(ll|[lhqL])?([cduxXefgsp%])/g;
+//               ▲         ▲                    ▲       ▲  ▲            ▲           ▲ type
+//               │         │                    │       │  │            └ Length (unsupported)
+//               │         │                    │       │  └ Precision / max width
+//               │         │                    │       └ Min width (unsupported)
+//               │         │                    └ Flags (unsupported)
+//               └ Index   └ Name (for named arguments)
+
+/**
+ * "Unordered" means there's no position specifier: '%s', not '%2$s'.
+ *
+ * @see https://github.com/WordPress/WordPress-Coding-Standards/blob/2f927b0ba2bfcbffaa8f3251c086e109302d6622/WordPress/Sniffs/WP/I18nSniff.php#L62-L81
+ *
+ * @type {RegExp}
+ */
+const REGEXP_SPRINTF_PLACEHOLDER_UNORDERED =
+	/(?:(?<!%)%[+-]?(?:(?:0|'.)?-?[0-9]*(?:\.(?:[ 0]|'.)?[0-9]+)?|(?:[ ])?-?[0-9]+(?:\.(?:[ 0]|'.)?[0-9]+)?)[bcdeEfFgGosuxX])/;
+
+module.exports = {
+	TRANSLATION_FUNCTIONS,
+	REGEXP_SPRINTF_PLACEHOLDER,
+	REGEXP_SPRINTF_PLACEHOLDER_UNORDERED,
+};

node_modules/@wordpress/eslint-plugin/utils/get-text-content-from-node.js

@@ -0,0 +1,34 @@
+/**
+ * Returns the actual text content from an argument passed to a translation function.
+ *
+ * @see eslint-plugin-wpcalypso
+ *
+ * @param {Object} node A Literal, TemplateLiteral or BinaryExpression (+) node
+ * @return {string|boolean} The concatenated string or false.
+ */
+function getTextContentFromNode( node ) {
+	if ( 'Literal' === node.type ) {
+		return node.value;
+	}
+
+	if ( 'BinaryExpression' === node.type && '+' === node.operator ) {
+		const left = getTextContentFromNode( node.left );
+		const right = getTextContentFromNode( node.right );
+
+		if ( left === false || right === false ) {
+			return false;
+		}
+
+		return left + right;
+	}
+
+	if ( node.type === 'TemplateLiteral' ) {
+		return node.quasis.map( ( quasis ) => quasis.value.raw ).join( '' );
+	}
+
+	return false;
+}
+
+module.exports = {
+	getTextContentFromNode,
+};

node_modules/@wordpress/eslint-plugin/utils/get-translate-function-args.js

@@ -0,0 +1,40 @@
+/**
+ * Given a function name and array of argument Node values,
+ * returns all arguments except for text domain and number arguments.
+ *
+ * @param {string}        functionName   Function name.
+ * @param {espree.Node[]} args           Espree argument Node objects.
+ * @param {boolean}       includeContext Whether to include the context argument or not.
+ *
+ * @return {espree.Node[]} Translate function arguments.
+ */
+function getTranslateFunctionArgs( functionName, args, includeContext = true ) {
+	switch ( functionName ) {
+		case '__':
+			// __( text, domain ) -> [ text ].
+			return args.slice( 0, 1 );
+
+		case '_x':
+			// _x( text, context, domain ) -> [ text, context ].
+			return includeContext ? args.slice( 0, 2 ) : args.slice( 0, 1 );
+
+		case '_n':
+			// _n( single, plural, number, domain ) -> [ single, plural ].
+			return args.slice( 0, 2 );
+
+		case '_nx':
+			// _nx( single, plural, number, context, domain ) -> [ single, plural, context ].
+			const result = args.slice( 0, 2 );
+			if ( includeContext ) {
+				result.push( args[ 3 ] );
+			}
+			return result;
+
+		default:
+			return [];
+	}
+}
+
+module.exports = {
+	getTranslateFunctionArgs,
+};

node_modules/@wordpress/eslint-plugin/utils/get-translate-function-name.js

@@ -0,0 +1,17 @@
+/**
+ * Get the actual translation function name from a CallExpression callee.
+ *
+ * Returns the "__" part from __ or i18n.__.
+ *
+ * @param {Object} callee
+ * @return {string} Function name.
+ */
+function getTranslateFunctionName( callee ) {
+	return callee.property && callee.property.name
+		? callee.property.name
+		: callee.name;
+}
+
+module.exports = {
+	getTranslateFunctionName,
+};

node_modules/@wordpress/eslint-plugin/utils/index.js

@@ -0,0 +1,22 @@
+/**
+ * Internal dependencies
+ */
+const {
+	TRANSLATION_FUNCTIONS,
+	REGEXP_SPRINTF_PLACEHOLDER,
+	REGEXP_SPRINTF_PLACEHOLDER_UNORDERED,
+} = require( './constants' );
+const { getTranslateFunctionArgs } = require( './get-translate-function-args' );
+const { getTextContentFromNode } = require( './get-text-content-from-node' );
+const { getTranslateFunctionName } = require( './get-translate-function-name' );
+const isPackageInstalled = require( './is-package-installed' );
+
+module.exports = {
+	TRANSLATION_FUNCTIONS,
+	REGEXP_SPRINTF_PLACEHOLDER,
+	REGEXP_SPRINTF_PLACEHOLDER_UNORDERED,
+	getTranslateFunctionArgs,
+	getTextContentFromNode,
+	getTranslateFunctionName,
+	isPackageInstalled,
+};

node_modules/@wordpress/eslint-plugin/utils/is-package-installed.js

@@ -0,0 +1,16 @@
+/**
+ * Checks whether the passed package name is installed in the project.
+ *
+ * @param {string} packageName The name of npm package.
+ * @return {boolean} Returns true when the package is installed or false otherwise.
+ */
+const isPackageInstalled = ( packageName ) => {
+	try {
+		if ( require.resolve( packageName ) ) {
+			return true;
+		}
+	} catch ( error ) {}
+	return false;
+};
+
+module.exports = isPackageInstalled;

node_modules/@wordpress/eslint-plugin/utils/test/is-package-installed.js

@@ -0,0 +1,18 @@
+/**
+ * Internal dependencies
+ */
+import isPackageInstalled from '../is-package-installed';
+
+describe( 'isPackageInstalled', () => {
+	test( 'returns false when package not installed', () => {
+		const result = isPackageInstalled( 'nonexistent-package-name' );
+
+		expect( result ).toBe( false );
+	} );
+
+	test( 'returns true when package installed', () => {
+		const result = isPackageInstalled( 'eslint' );
+
+		expect( result ).toBe( true );
+	} );
+} );