fix(app): guard missing notification server state

[jones]

Issue for this PR

Closes #35686

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Prevents the app notification context from crashing the renderer when notification state is requested for a server key that is not present in the current server list.

I hit this in OpenCode Desktop v1.17.14 on macOS. After startup, the app entered an infinite crash loop with:

Error: Notification server not found: http://[server-ip]:4096

Restart and Reload Webview did not clear it; the same error returned on the next launch. The IP address is an OpenCode server on my local network, and I can connect to it normally.

The crash started after a hard reset on macOS 27.0 beta. The entire macOS UI froze, so I forced a restart. After that, OpenCode Desktop was stuck showing this startup error and could not be used.

This change makes missing notification server state degrade to an empty/no-op notification state instead of throwing during render. Notification badges may be absent for that stale server key, but the app remains usable.

How did you verify your code works?

Ran:

npm exec --yes --package bun@1.3.14 -- bun run typecheck
npm exec --yes --package bun@1.3.14 -- bun run test:unit

Both passed from packages/app.

Screenshots / recordings

Before:

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR