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/README.md

@@ -0,0 +1,108 @@
+# ESLint Plugin
+
+[ESLint](https://eslint.org/) plugin including configurations and custom rules for WordPress development.
+
+## Installation
+
+Install the module
+
+```bash
+npm install @wordpress/eslint-plugin --save-dev
+```
+
+**Note**: This package requires `node` 14.0.0 or later, and `npm` 6.14.4 or later. It is not compatible with older versions.
+
+## Usage
+
+To opt-in to the default configuration, extend your own project's `.eslintrc` file:
+
+```json
+{
+	"extends": [ "plugin:@wordpress/eslint-plugin/recommended" ]
+}
+```
+
+Refer to the [ESLint documentation on Shareable Configs](http://eslint.org/docs/developer-guide/shareable-configs) for more information.
+
+The `recommended` preset will include rules governing an ES2015+ environment, and includes rules from the [`eslint-plugin-jsdoc`](https://github.com/gajus/eslint-plugin-jsdoc), [`eslint-plugin-jsx-a11y`](https://github.com/jsx-eslint/eslint-plugin-jsx-a11y), [`eslint-plugin-react`](https://github.com/yannickcr/eslint-plugin-react), and other similar plugins.
+
+This preset offers an optional integration with the [`eslint-plugin-prettier`](https://github.com/prettier/eslint-plugin-prettier) package that runs [Prettier](https://prettier.io) code formatter and reports differences as individual ESLint issues. You can activate it by installing the [`prettier`](https://www.npmjs.com/package/prettier) package separately with:
+
+```bash
+npm install prettier --save-dev
+```
+
+Finally, this ruleset also includes an optional integration with the [`@typescript-eslint/eslint-plugin`](https://github.com/typescript-eslint/typescript-eslint) package that enables ESLint to support [TypeScript](https://www.typescriptlang.org) language. You can activate it by installing the [`typescript`](https://www.npmjs.com/package/typescript) package separately with:
+
+```bash
+npm install typescript --save-dev
+```
+
+There is also `recommended-with-formatting` ruleset for projects that want to ensure that [Prettier](https://prettier.io) and [TypeScript](https://www.typescriptlang.org) integration is never activated. This preset has the native ESLint code formatting rules enabled instead.
+
+### Rulesets
+
+Alternatively, you can opt-in to only the more granular rulesets offered by the plugin. These include:
+
+-   `custom` – custom rules for WordPress development.
+-   `es5` – rules for legacy ES5 environments.
+-   `esnext` – rules for ES2015+ environments.
+-   `i18n` – rules for internationalization.
+-   `jsdoc` – rules for JSDoc comments.
+-   `jsx-a11y` – rules for accessibility in JSX.
+-   `react` – rules for React components.
+-   `test-e2e` – rules for end-to-end tests written in Puppeteer.
+-   `test-unit`– rules for unit tests written in Jest.
+-   `test-playwright` – rules for end-to-end tests written in Playwright.
+
+For example, if your project does not use React, you could consider extending including only the ESNext rules in your project using the following `extends` definition:
+
+```json
+{
+	"extends": [ "plugin:@wordpress/eslint-plugin/esnext" ]
+}
+```
+
+These rules can be used additively, so you could extend both `esnext` and `custom` rulesets, but omit the `react` and `jsx-a11y` configurations.
+
+The granular rulesets will not define any environment globals. As such, if they are required for your project, you will need to define them yourself.
+
+### Rules
+
+| Rule                                                                                                                                                                 | Description                                                                                    | Recommended |
+| -------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- | ----------- |
+| [data-no-store-string-literals](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/data-no-store-string-literals.md)                 | Discourage passing string literals to reference data stores                                    |             |
+| [dependency-group](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/dependency-group.md)                                           | Enforce dependencies docblocks formatting                                                      | ✓           |
+| [is-gutenberg-plugin](docs/rules/is-gutenberg-plugin.md)                                                                                                             | Governs the use of the `process.env.IS_GUTENBERG_PLUGIN` constant                              | ✓           |
+| [no-base-control-with-label-without-id](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/no-base-control-with-label-without-id.md) | Disallow the usage of BaseControl component with a label prop set but omitting the id property | ✓           |
+| [no-unguarded-get-range-at](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/no-unguarded-get-range-at.md)                         | Disallow the usage of unguarded `getRangeAt` calls                                             | ✓           |
+| [no-unsafe-wp-apis](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/no-unsafe-wp-apis.md)                                         | Disallow the usage of unsafe APIs from `@wordpress/*` packages                                 | ✓           |
+| [no-unused-vars-before-return](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/no-unused-vars-before-return.md)                   | Disallow assigning variable values if unused before a return                                   | ✓           |
+| [react-no-unsafe-timeout](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/react-no-unsafe-timeout.md)                             | Disallow unsafe `setTimeout` in component                                                      |             |
+| [valid-sprintf](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/valid-sprintf.md)                                                 | Enforce valid sprintf usage                                                                    | ✓           |
+| [i18n-ellipsis](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-ellipsis.md)                                                 | Disallow using three dots in translatable strings                                              | ✓           |
+| [i18n-no-collapsible-whitespace](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-no-collapsible-whitespace.md)               | Disallow collapsible whitespace in translatable strings                                        | ✓           |
+| [i18n-no-placeholders-only](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-no-placeholders-only.md)                         | Prevent using only placeholders in translatable strings                                        | ✓           |
+| [i18n-no-variables](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-no-variables.md)                                         | Enforce string literals as translation function arguments                                      | ✓           |
+| [i18n-text-domain](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-text-domain.md)                                           | Enforce passing valid text domains                                                             | ✓           |
+| [i18n-translator-comments](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-translator-comments.md)                           | Enforce adding translator comments                                                             | ✓           |
+| [i18n-no-flanking-whitespace](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-no-flanking-whitespace.md)                     | Disallow leading or trailing whitespace in translatable strings                                |             |
+| [i18n-hyphenated-range](https://github.com/WordPress/gutenberg/tree/HEAD/packages/eslint-plugin/docs/rules/i18n-hyphenated-range.md)                                 | Disallow hyphenated numerical ranges in translatable strings                                   |             |
+
+### Legacy
+
+If you are using WordPress' `.jshintrc` JSHint configuration and you would like to take the first step to migrate to an ESLint equivalent it is also possible to define your own project's `.eslintrc` file as:
+
+```json
+{
+	"extends": [ "plugin:@wordpress/eslint-plugin/jshint" ]
+}
+```
+
+## Contributing to this package
+
+This is an individual package that's part of the Gutenberg project. The project is organized as a monorepo. It's made up of multiple self-contained software packages, each with a specific purpose. The packages in this monorepo are published to [npm](https://www.npmjs.com/) and used by [WordPress](https://make.wordpress.org/core/) as well as other software projects.
+
+To find out more about contributing to this package or Gutenberg as a whole, please read the project's main [contributor guide](https://github.com/WordPress/gutenberg/tree/HEAD/CONTRIBUTING.md).
+
+<br /><br /><p align="center"><img src="https://s.w.org/style/images/codeispoetry.png?1" alt="Code is Poetry." /></p>