chore: upgrade eslint to v9

eslint.config.js

@@ -0,0 +1,69 @@
+import eslint from '@eslint/js';
+import tseslint from '@typescript-eslint/eslint-plugin';
+import tsparser from '@typescript-eslint/parser';
+import globals from 'globals';
+import importPlugin from 'eslint-plugin-import';
+
+export default [
+  {
+    ignores: [
+      '**/__tests__/**',
+      'packages/*/lib/**',
+      '*.js',
+      'packages/respect-core/src/modules/runtime-expressions/abnf-parser.js', // Generated file
+    ],
+  },
+  eslint.configs.recommended,
+  {
+    files: ['**/*.ts'],
+    languageOptions: {
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+      parser: tsparser,
+      globals: {
+        ...globals.browser,
+        ...globals.node,
+        ...globals.es2021,
+      },
+    },
+    plugins: {
+      '@typescript-eslint': tseslint,
+      import: importPlugin,
+    },
+    rules: {
+      // TypeScript ESLint recommended rules
+      ...tseslint.configs.recommended.rules,
+      // Custom overrides
+      'no-undef': 'off', // TypeScript handles this better
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          varsIgnorePattern: '^_',
+          caughtErrors: 'none', // Don't check unused catch clause variables
+        },
+      ],
+      '@typescript-eslint/no-var-requires': 'off',
+      '@typescript-eslint/no-empty-function': 'off',
+      '@typescript-eslint/no-inferrable-types': 'off',
+      // Note: @typescript-eslint/ban-types was removed in v8, replaced by @typescript-eslint/no-unsafe-function-type
+      '@typescript-eslint/no-explicit-any': 'warn',
+      'no-prototype-builtins': 'off',
+      'no-useless-escape': 'error',
+      '@typescript-eslint/consistent-type-imports': [
+        'error',
+        {
+          prefer: 'type-imports',
+        },
+      ],
+      'import/order': [
+        'error',
+        {
+          groups: [['builtin', 'external', 'parent', 'sibling', 'index', 'object'], ['type']],
+          'newlines-between': 'always',
+        },
+      ],
+      'import/no-duplicates': 'error',
+    },
+  },
+];