## Summary
- Adds new "Auto-expand preview panel" toggle in Workflow Settings
- When disabled, the preview panel stays collapsed after chat responses
and proposal approvals
- Defaults to enabled to preserve existing behavior

Fixes #2090

## Test plan
1. Go to Settings > Workflow Settings
2. Disable "Auto-expand preview panel"
3. Collapse the preview panel manually
4. Send a chat message that generates code changes
5. Verify the preview panel stays collapsed

🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- devin-review-badge-begin -->

---

<a href="https://app.devin.ai/review/dyad-sh/dyad/pull/2352">
  <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 -->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduces a user setting to control automatic preview expansion after
code changes.
> 
> - Adds `autoExpandPreviewPanel` to `UserSettings` with default `true`
and schema support
> - New `AutoExpandPreviewSwitch` and integrates it into Workflow
Settings UI
> - Gates preview opening in `ChatInput` (on approve) and
`useStreamChat` (on stream end) behind the new setting
> - Updates settings defaults and unit tests to include the new field
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
74064a7eb9092556833afd8fcb37527e59de14cc. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Adds an “Auto-expand preview panel” toggle in Workflow Settings to
control whether the preview opens automatically after chat file updates
or proposal approvals. Defaults to on to preserve current behavior and
addresses Linear issue #2090.

<sup>Written for commit 74064a7eb9092556833afd8fcb37527e59de14cc.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>