Migrate to ESLint 9 flat config, replace vscode-test with @vscode/test-electron, and add GitHub Actions CI

.github/workflows/ci.yml

@@ -0,0 +1,39 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build-and-test:
+    name: Build, Lint & Test
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build (esbuild)
+        run: npm run esbuild
+
+      - name: Lint
+        run: npm run lint
+
+      - name: TypeScript compile
+        run: npm run ts-compile
+
+      - name: Unit tests
+        run: npm run unit-test

eslint.config.mjs

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+// @ts-check
+import tseslint from 'typescript-eslint';
+
+export default tseslint.config(
+	{
+		ignores: ['**/src/*/vscode.d.ts', '**/src/*/vscode.proposed*.d.ts', 'out/', 'dist/'],
+	},
+	{
+		files: ['src/**/*.ts'],
+		plugins: {
+			'@typescript-eslint': tseslint.plugin,
+		},
+		languageOptions: {
+			parser: tseslint.parser,
+			parserOptions: {
+				ecmaVersion: 6,
+				sourceType: 'module',
+			},
+		},
+		rules: {
+			'constructor-super': 'warn',
+			'curly': 'warn',
+			'eqeqeq': 'warn',
+			'no-caller': 'warn',
+			'no-debugger': 'warn',
+			'no-duplicate-case': 'warn',
+			'no-duplicate-imports': 'warn',
+			'no-eval': 'warn',
+			'no-extra-semi': 'warn',
+			'no-new-wrappers': 'warn',
+			'no-sparse-arrays': 'warn',
+			'no-throw-literal': 'warn',
+			'no-unsafe-finally': 'warn',
+			'no-unused-labels': 'warn',
+			'no-var': 'warn',
+		},
+	}
+);