Bump eslint from 8.57.0 to 9.38.0

Migrate from .eslintrc.json to eslint.config.mjs (flat config) as
required by ESLint 9. Adapt rule names for eslint-plugin-github's
flat config format (importPlugin/ prefix).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hsbt

.eslintignore

@@ -0,0 +1,70 @@
+import github from 'eslint-plugin-github'
+import jest from 'eslint-plugin-jest'
+import tseslint from 'typescript-eslint'
+
+const githubConfigs = github.getFlatConfigs()
+
+export default tseslint.config(
+  {
+    ignores: ['dist/', 'lib/', 'node_modules/', 'jest.config.js']
+  },
+  githubConfigs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    files: ['**/*.ts'],
+    plugins: {
+      jest
+    },
+    languageOptions: {
+      parserOptions: {
+        ecmaVersion: 9,
+        sourceType: 'module',
+        project: './tsconfig.json'
+      }
+    },
+    rules: {
+      'filenamesPlugin/match-regex': 'off',
+      'i18n-text/no-en': 'off',
+      'eslint-comments/no-use': 'off',
+      'import/no-namespace': 'off',
+      'importPlugin/no-namespace': 'off',
+      'importPlugin/no-unresolved': 'off',
+      'no-unused-vars': 'off',
+      '@typescript-eslint/no-unused-vars': 'error',
+      '@typescript-eslint/explicit-member-accessibility': [
+        'error',
+        {accessibility: 'no-public'}
+      ],
+      '@typescript-eslint/no-require-imports': 'error',
+      '@typescript-eslint/array-type': 'error',
+      '@typescript-eslint/await-thenable': 'error',
+      '@typescript-eslint/ban-ts-comment': 'error',
+      camelcase: 'off',
+      '@typescript-eslint/consistent-type-assertions': 'error',
+      '@typescript-eslint/explicit-function-return-type': [
+        'error',
+        {allowExpressions: true}
+      ],
+      '@typescript-eslint/no-array-constructor': 'error',
+      '@typescript-eslint/no-explicit-any': 'error',
+      '@typescript-eslint/no-extraneous-class': 'error',
+      '@typescript-eslint/no-for-in-array': 'error',
+      '@typescript-eslint/no-inferrable-types': 'error',
+      '@typescript-eslint/no-misused-new': 'error',
+      '@typescript-eslint/no-namespace': 'error',
+      '@typescript-eslint/no-non-null-assertion': 'warn',
+      '@typescript-eslint/no-unnecessary-qualifier': 'error',
+      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
+      '@typescript-eslint/no-useless-constructor': 'error',
+      '@typescript-eslint/prefer-for-of': 'warn',
+      '@typescript-eslint/prefer-function-type': 'warn',
+      '@typescript-eslint/prefer-includes': 'error',
+      '@typescript-eslint/prefer-string-starts-ends-with': 'error',
+      '@typescript-eslint/promise-function-async': 'error',
+      '@typescript-eslint/require-array-sort-compare': 'error',
+      '@typescript-eslint/restrict-plus-operands': 'error',
+      semi: 'off',
+      '@typescript-eslint/unbound-method': 'error'
+    }
+  }
+)