fix: Fix stop issue when stop in the UI - stop in the mastra BE

[KayTV]

This pull request introduces a new mechanism for stopping chat sessions, specifically enhancing support for the "web automation" chat model. The main changes include adding a custom stop function in the chat component that sends a stopChat action to the backend, and updating the API route to handle this new action by forwarding the stop request to the Mastra backend.

Changes

• Added a custom stop function in components/chat.tsx that, for the web-automation-model, sends a stopChat action to the backend with the relevant threadId and resourceId, in addition to aborting the chat stream locally.
• Updated the destructuring in components/chat.tsx to rename the original stop function to originalStop, allowing for the custom logic to be added.
• Modified app/(chat)/api/mastra-proxy/route.ts to handle requests with action: 'stopChat', forwarding them to the Mastra backend's /stop-chat endpoint and returning the backend's response.

Testing

[fg-nava]

Approved but left a comment to review the other artifacts that our chatbot template made available.

[fg-nava]

I just want to verify we've reviewed the other artifacts that are available in the AI Chatbot template (like the table artifact). I recall seeing stop controls there as well albeit they were not using App Router to send POSTs to a Mastra backend. Little doffeeent but there is a possibility we can adhere to the same pattern.

[fg-nava]

Just realized you are probably wanting to hold on merging this until the pilot is over, right? Should we create a staging branch here? @KayTV