<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Adds an informational toast to guide users when enabling the new agent
mode.
> 
> - New `LocalAgentNewChatToast` with dismiss and "Never show again"
actions (auto-dismiss after 8s)
> - `ChatModeSelector`: when switching to `local-agent` on `/chat` with
existing messages, show the toast using `sonner`; uses TanStack Router
for route detection and Jotai chat state
> - `UserSettingsSchema`: adds `hideLocalAgentNewChatToast` to persist
user preference
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
b07beac9d13b87b2e08ea1a9a376994148beb6c9. 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
Shows a friendly info toast when switching to Agent mode on the chat
page, encouraging a fresh chat for better results. Includes dismiss and
“never show again” options that respect user preferences.

- **New Features**
- Added LocalAgentNewChatToast, shown when selecting local-agent on
/chat with existing messages.
- “Never show again” persists via hideLocalAgentNewChatToast in
UserSettingsSchema.
- Uses TanStack Router to detect the chat route; toast auto-dismisses
after 8s.

<sup>Written for commit b07beac9d13b87b2e08ea1a9a376994148beb6c9.
Summary will update on new commits.</sup>

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