chore: add openui repository metadata (#2616)

## Summary

Adds the missing `repository` metadata to
`packages/genui/openui/package.json`, matching the format used by other
packages in the monorepo.

## Impact

Consumers and package metadata tooling can resolve the package back to
the Lynx Stack repository and package directory.

## Validation

- `node -e
"JSON.parse(require('node:fs').readFileSync('packages/genui/openui/package.json','utf8'));
console.log('package.json OK')"`
- `git diff --check HEAD^ HEAD -- packages/genui/openui/package.json`
- `node_modules/.bin/dprint check packages/genui/openui/package.json`


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
  * Updated package repository metadata.

[![Review Change
Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/lynx-family/lynx-stack/pull/2616)

<!-- end of auto-generated comment: release notes by coderabbit.ai -->