Disable Cache Components by default for chat shell

[garinyan]

Fixes #1501.

Summary

This disables Cache Components / PPR by default for the chatbot template by removing:

• cacheComponents: true
• experimental.cachedNavigations: true

Root cause

In Next.js 16, cacheComponents: true opts the app into Cache Components / Partial Prerendering behavior, and experimental.cachedNavigations depends on that mode. The chat shell reads request-time data such as auth() and cookies(), so enabling PPR by default can cause a deployment to serve the homepage as a raw application/x-nextjs-pre-render payload rather than normal HTML. In that failure mode the request returns HTTP 200, but the page renders internal pre-render payload text instead of the chat UI.

This PR intentionally does not migrate the whole app to Cache Components/PPR. That would require a broader audit of request-time data access, Suspense boundaries, and cache semantics. The safer default for the template is to keep these experimental/PPR-related knobs off unless an app owner opts in explicitly.

Testing

• pnpm check

I also attempted pnpm build locally, but this Codex macOS environment cannot load the Next.js native SWC binary due to a local code-signing issue:

Failed to load SWC binary for darwin/arm64

That failure happens while loading Next/SWC and is unrelated to this config diff.

[vercel]

@garinyan is attempting to deploy a commit to the Templates Test vtest314 Team on Vercel.

A member of the Team first needs to authorize it.

[garinyan]

Follow-up status note: the code-related checks currently reported on this PR are passing. The two failing Vercel statuses are authorization gates for preview deployments from a fork:

• Vercel – ai-chatbot: Authorization required to deploy
• Vercel – chatbot: Authorization required to deploy

A member of the corresponding Vercel team will need to authorize those deployments before the preview checks can run.