chore: dogfood defineConfig() now that exadevConfig() satisfies it

eslint.config.ts

@@ -1,8 +1,9 @@
+import { defineConfig } from 'eslint/config';
 import js from '@eslint/js';
 import { exadevConfig } from './src/index';
 
-// A plain flat-config array, not wrapped in `tseslint.config(...)` (now `@deprecated` in favour of ESLint core's own `defineConfig()`, per typescript-eslint's own doc comment) nor in `defineConfig(...)` (whose parameter type is `@eslint/core`'s `ConfigObject`, which declares an explicit string index signature that `@typescript-eslint/utils`'s `TSESLint.FlatConfig.Config` -- the type this config's own elements carry -- does not; TypeScript refuses that assignment outright, and this codebase bans the `as` cast that would paper over it). ESLint's flat-config loader only ever required a plain array (or object, or array-of-arrays) as the default export -- both helpers exist purely for `extends`-flattening and stricter typing neither of which this already-flat array needs -- so this sidesteps the deprecated call and the cross-package type gap at once, rather than working around either.
-export default [
+// defineConfig() over a plain array or the now-@deprecated tseslint.config(): exadevConfig()'s return type is PublicConfigArray (see src/config-types.ts), typed against @eslint/core's own ConfigObject specifically so it satisfies defineConfig()'s parameter type directly -- this file is the first real proof of that, dogfooding the fix on the same repo that ships it.
+export default defineConfig(
   {
     ignores: ['dist', 'coverage', 'node_modules', '.turbo'],
   },
@@ -31,4 +32,4 @@ export default [
     files: ['src/consumer-compatibility.ts'],
     rules: { '@typescript-eslint/no-deprecated': 'off' },
   },
-];
+);