Merge branch 'shuvcode-dev' into integration

Fix bunfig preload conflict via postinstall symlink (#245)

- Add postinstall.mjs with platform detection and baseline variant fallback
- Update build.ts to enable autoloadTsconfig and autoloadPackageJson
- Update publish.ts to include postinstall.mjs in published package
- Add planning document for issue #245

Closes #252

Author: shuv1337