Adding @module-federation/vite breaks vanilla @tanstack start project

Which project does this relate to?

Start

Describe the bug

After generating a new project, adding @module-federation/vite breaks the build.

Similar to #4516

Your Example Website or App

https://github.com/jsg2021/tanstack-start-module-federation-issue

Steps to Reproduce the Bug or Issue

run build

Expected behavior

Build succeeds with normal output plus federated assets

This check probably needs to be more sophisticated: https://github.com/TanStack/router/blob/b1c0f4602df7d3950df199e6471774f0520a359b/packages/start-plugin-core/src/start-manifest-plugin/manifestBuilder.ts#L195-L200

We can produce multiple "entry" points... Is there a way to flag which one we want in this context?

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.167.6
• OS: macOS/Linux
• Browser: irrelevant, in terminal.
• Bundler: Vite
• Bundler Version: 7.3.1

Additional context

No response

Start with the linked reproduction repository and run its build command to observe how adding @module-federation/vite fails. Read packages/start-plugin-core/src/start-manifest-plugin/manifestBuilder.ts around lines 195-200, focusing on how multiple entry points are handled. Done means a generated Start project builds successfully with normal output and federated assets.