feat(onboarding): Add guide for setup without --import to tanstack start

[nicohrubec]

Update the in-product onboarding to point to the docs guide for cases where users cannot set --import. Also add the server entry point instructions also if tracing is not selected. Right now that is not necessary for node but eventually we will do error monitoring in there so I'd rather tell users to already add this.

Docs PR

[andreiborza]

@nicohrubec I don't think we should document the "serverless' approach in onboarding. It's something we can do a much better job of in the docs. Onboarding is kind of for the happy-path and everything more complicated can stay in the docs.

Also, just to make sure, do you mean platform providers like vercel and netlify by "serverless"? Traditionally, that term refers to stuff like aws lambda and other cloud functions.

[nicohrubec]

@andreiborza Why not document this here as well? As a user I'd be annoyed if I set this up as described in the onboarding and then it doesn't work so I have to go to the docs to get the actual guide. I think we should at least have a reference to the docs then to say that if you can't use --import in your setup you should follow the docs

[andreiborza]

@nicohrubec fair, I just think it's overwhelming and always difficult to keep aligned. I like your suggestion of linking to the docs instead.

Eventually, we'll replace the onboarding flow with the wizard and then we'll just link to docs as an alternative anyway.

[nicohrubec]

@andreiborza sounds good! removed the full guide and added the link to the docs

[andreiborza]

Maybe we could link directly to platforms/javascript/guides/tanstackstart-react/#without---import-flag-eg-vercel-netlify? wdyt?