Update to latest ESLint and @typescript-eslint packages with flat config migration

[Copilot]

Bumps @typescript-eslint/* from alpha (^8.0.0-alpha.54) to stable ^8.0.0, updates ESLint peer dependency to ^9.0.0 || ^10.0.0, and migrates configs from legacy eslintrc format to ESLint flat config — required for ESLint 10 compatibility.

Dependency changes (package.json)

• @typescript-eslint/eslint-plugin / parser: ^8.0.0-alpha.54 → ^8.0.0
• eslint: ^9.7.0 → ^9.0.0 || ^10.0.0
• Added @eslint/js: ^9.0.0 || ^10.0.0 — provides js.configs.recommended for flat config
• Added globals: >=14.0.0 — replaces the legacy env block for browser/node/es2015 globals

core.js — flat config array

Replaces the single legacy eslintrc export with a flat config array using @typescript-eslint's new flat/ config entries:

// Before (legacy format)
module.exports = {
  extends: ['eslint:recommended', 'plugin:@typescript-eslint/recommended-type-checked', ...],
  parser: '@typescript-eslint/parser',
  env: { browser: true, es6: true, node: true },
  ...
};

// After (flat config)
module.exports = [
  js.configs.recommended,
  ...tsPlugin.configs['flat/recommended-type-checked'],
  ...tsPlugin.configs['flat/stylistic-type-checked'],
  prettier,
  { plugins, languageOptions: { globals, parser: tsParser, parserOptions: { project: './tsconfig.json' } }, rules }
];

index.js — React flat config

Replaces mutation of the core export with a proper flat config array, using eslint-plugin-react's configs.flat.recommended (available since v7.33):

module.exports = [
  ...core,
  reactPlugin.configs.flat['recommended'],
  { rules: { 'react/no-unstable-nested-components': ['warn', { allowAsProps: true }] }, settings: { react: { version: 'detect' } } }
];

README.md

Updated usage examples from legacy extends: [...] to eslint.config.js flat config spread pattern.