Agent Playground continually fetches `/instance_name` regardless of connection status

[deankerr]

The web app appears to be stuck in an infinite loop making a call to the instance_name endpoint. This appears to occur whether or not it has found a deployment, or if the user has successfully logged in with an API key.

Steps to reproduce:

1. Create a new Convex app: npm create convex@latest my-app -- -t bare
2. (Optional) Install and configure the agent component package, create the playground.ts endpoint and API key as described in the docs
3. Run npm run dev, configure a cloud or local deployment, deploy functions
4. Run npx @convex-dev/agent-playground and view the Agent Playground login screen in Chrome
5. Open the devtools Network tab and observe the repeating requests to /instance_name
6. (Optional) Log in to the playground with a valid key, and observe the repeating requests

This happens with both cloud and local deployments, but with local deployments the requests appear to happen at ~2x speed.