fix: prevent unnecessary __data.json requests

[Rich-Harris]

This will close #7967
Also fixes #8655

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[arackaf]

👀

[benmccann]

Why do we need to swap the order of the builds? One concern I have with that is that we've gotten requests not to do the server-side build for SPAs, etc. That becomes harder if the server-side build is the primary build

[Rich-Harris]

You can't not do the server side build! Just because you're not rendering the body content doesn't mean you don't need a server.

The server needs to go first because the client manifest needs to know which nodes have server loads. We can't know that without doing the server build (and analysing it) before the client build.

[benmccann]

If you're building a SPA with fallback page and no server side endpoints, what do you need the server for exactly?

[Rich-Harris]

To generate the fallback page (while respecting things like transformPageChunk)

[dummdidumm]

The CI fail seems to be consistent. Failed two times on Mac, both times with an error hinting that writeBundle did not resolve correctly (or in time?).

[Rich-Harris]

Hmm. The most likely explanation for that would be that the cross-process communication failed for some reason and the promise never resolved, which makes me nervous