## Summary
- Add ADR 0001 for host capability interface decisions.
- Add ADR 0002 for cloud runtime topology and ADR 0003 for authz model.
- Add ADR index and architecture updates for cross-platform planning.
- Add desktop/mobile/web unification plan document in plans/.

## Test plan
- npm run fmt
- npm run lint:fix
- npm run ts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- devin-review-badge-begin -->

---

<a href="https://app.devin.ai/review/dyad-sh/dyad/pull/2737"
target="_blank">
  <picture>
<source media="(prefers-color-scheme: dark)"
srcset="https://static.devin.ai/assets/gh-open-in-devin-review-dark.svg?v=1">
<img
src="https://static.devin.ai/assets/gh-open-in-devin-review-light.svg?v=1"
alt="Open with Devin">
  </picture>
</a>
<!-- devin-review-badge-end -->

---------
Co-authored-by: wwwillchen-bot <theodorewilsonchen@gmail.com>