Unify linting: replace Stylelint and markdownlint with ESLint

.github/CONTRIBUTING.md

@@ -8,25 +8,10 @@ We hold our code to standard, and these standards are documented below.
 
 We use [prettier](https://prettier.io/) for automatic formatting a lot all our files. The configuration is in our `prettier.config.mjs` file.
 
-To run prettier, use `node --run lint:prettier`.
+And we use [ESLint](https://eslint.org) to lint our JavaScript, Markdown, and CSS files. The configuration is in our `eslint.config.mjs` file.
 
-### JavaScript: Run ESLint
-
-We use [ESLint](https://eslint.org) to lint our JavaScript files. The configuration is in our `eslint.config.mjs` file.
-
-To run ESLint, use `node --run lint:js`.
-
-### CSS: Run StyleLint
-
-We use [StyleLint](https://stylelint.io) to lint our CSS. The configuration is in our `stylelint.config.mjs` file.
-
-To run StyleLint, use `node --run lint:css`.
-
-### Markdown: Run markdownlint
-
-We use [markdownlint-cli2](https://github.com/DavidAnson/markdownlint-cli2) to lint our markdown files. The configuration is in our `.markdownlint.json` file.
-
-To run markdownlint, use `node --run lint:markdown`.
+To check for formatting and linting errors, use `node --run test:lint`
+To fix formatting and linting errors, use `node --run lint:fix`.
 
 ## Testing
 
@@ -43,6 +28,7 @@ The `package.json` scripts expose finer-grained test commands:
 - `test:watch` – keep Vitest in watch mode for fast local feedback
 - `test:ui` – open the Vitest UI dashboard (needs OS file-watch support enabled)
 - `test:calendar` – run the legacy calendar debug helper
-- `test:css`, `test:markdown`, `test:prettier`, `test:spelling`, `test:js` – lint-only scripts that enforce formatting, spelling, markdown style, and ESLint.
+- `test:lint` – run linter and formatter checks
+- `test:spelling` – run the spell checker
 
 You can invoke any script with `node --run <script>` (or `npm run <script>`). Individual files can still be targeted directly, e.g. `npx vitest run tests/e2e/env_spec.js`.

.github/PULL_REQUEST_TEMPLATE.md

@@ -10,7 +10,7 @@ Hello and thank you for wanting to contribute to the MagicMirror² project!
 > - What does the pull request accomplish? Use a list if needed.
 > - If it includes major visual changes please add screenshots.
 >
-> 3. Please run `node --run lint:prettier` before submitting so that
+> 3. Please run `node --run lint:fix` before submitting so that
 >    style issues are fixed.
 
 **Note**: Sometimes the development moves very fast. It is highly

.github/workflows/automated-tests.yaml

@@ -33,10 +33,7 @@ jobs:
           node --run install-mm:dev
       - name: "Run linter tests"
         run: |
-          node --run test:prettier
-          node --run test:js
-          node --run test:css
-          node --run test:markdown
+          node --run test:lint
   test:
     runs-on: ubuntu-24.04
     timeout-minutes: 30

cspell.config.json

@@ -290,7 +290,6 @@
 		"sthuber",
 		"Stieber",
 		"strinner",
-		"stylelintrc",
 		"sunaction",
 		"suncalc",
 		"suntimes",

eslint.config.mjs

@@ -1,15 +1,36 @@
 import {defineConfig, globalIgnores} from "eslint/config";
+import css from "@eslint/css";
 import globals from "globals";
 import {flatConfigs as importX} from "eslint-plugin-import-x";
 import js from "@eslint/js";
 import jsdocPlugin from "eslint-plugin-jsdoc";
+import markdown from "@eslint/markdown";
 import {configs as packageJsonConfigs} from "eslint-plugin-package-json";
 import playwright from "eslint-plugin-playwright";
 import stylistic from "@stylistic/eslint-plugin";
 import vitest from "@vitest/eslint-plugin";
 
 export default defineConfig([
 	globalIgnores(["config/**", "modules/**/*", "js/positions.js", "tests/configs/config_variables.js"]),
+	{
+		files: ["**/*.css"],
+		language: "css/css",
+		plugins: {css},
+		extends: ["css/recommended"],
+		rules: {
+			"css/no-invalid-properties": ["error", {allowUnknownVariables: true}],
+			"css/use-baseline": "off"
+		}
+	},
+	{
+		files: ["**/*.md"],
+		plugins: {markdown},
+		language: "markdown/gfm",
+		extends: ["markdown/recommended"],
+		rules: {
+			"markdown/no-missing-label-refs": "off"
+		}
+	},
 	{
 		files: ["**/*.js"],
 		languageOptions: {