### Description

Similar to #10794, adding in
some sanity checks before we do some refactors to improve these
packages.

### Testing Instructions

CI

Fixes #10901

In PR #10794, we changed from module.exports to export default, which
caused bunchee to generate exports.default = config instead of
module.exports = config in the CommonJS build.

ESLint v8 with legacy .eslintrc.* configuration expects shareable
configs to export directly via module.exports. When it encounters
exports.default, it interprets 'default' as an unexpected top-level
configuration property, resulting in the error:
'Unexpected top-level property "default"'

This fix reverts to module.exports for the main entry point to restore
ESLint v8 compatibility, while maintaining ESLint v9 flat config support
through the ./flat export path.

Testing:
- Verified publint --strict passes
- Verified attw type checking passes
- Confirmed compiled output uses module.exports
- Both CJS require() and ESM import() work correctly

…ity (#10902)

### Description

Fixes #10901

In PR #10794, we changed from `module.exports` to `export default`,
which caused bunchee to generate `exports.default = config` instead of
`module.exports = config` in the CommonJS build.

ESLint v8 with legacy `.eslintrc.*` configuration expects shareable
configs to export directly via `module.exports`. When it encounters
`exports.default`, it interprets `'default'` as an unexpected top-level
configuration property, resulting in the error:

```
Unexpected top-level property "default"
```

### Changes

1. **`packages/eslint-config-turbo/src/index.ts`**
- Reverted from `export default config;` to `module.exports = config;`
- Ensures compiled CommonJS output properly exports the config object
directly

2. **`packages/eslint-config-turbo/package.json`**
- Removed the `module` field (no longer generating ESM for main entry)
- Updated `exports[".'"]` to point both `import` and `require` to the
CommonJS build
- Maintains compatibility while ensuring ESLint v8 can properly load the
configuration

### Why This Fixes The Problem

- **Before**: Using `export default` caused bunchee to generate
`exports.default = config;`
- **After**: Using `module.exports` generates `module.exports = config;`
which is what ESLint v8 expects
- ESLint v9 flat config support is maintained through the separate
`./flat` export path

### Testing Instructions

1. Build the package: `pnpm --filter=eslint-config-turbo build`
2. Run package validation: `pnpm --filter=eslint-config-turbo
package:lint`
3. Run type checking: `pnpm --filter=eslint-config-turbo package:types`
4. Verify compiled output: `cat
packages/eslint-config-turbo/dist/cjs/index.js` (should show
`module.exports = config;`)

All checks pass:
- ✅ `publint --strict`
- ✅ `attw --profile node16 --pack`
- ✅ `pnpm lint`
- ✅ Correct CommonJS output

### Compatibility

- ✅ **ESLint v8 (legacy config)**: Uses `require('eslint-config-turbo')`
- now works correctly
- ✅ **ESLint v9 (flat config)**: Uses `import turboConfig from
'eslint-config-turbo/flat'` - continues to work
- ✅ **Modern bundlers**: Can import from either path

CLOSES TURBO-4861

---------

Co-authored-by: pauloZion <paulozionpazi@gmail.com>