Non-GET shadow endpoint status response not respected

[Conduitry]

Describe the bug

Returning an error status (4xx/5xx) from a non-GET shadow endpoint is not properly being inherited by the final rendered page, which is always a 200 (assuming the implicit GET afterwards succeeded).

Reproduction

https://github.com/Conduitry-Repros/kit-3721

Logs

No response

System Info

System:
    OS: Linux 5.10 Ubuntu 20.04.3 LTS (Focal Fossa)
    CPU: (8) x64 Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
    Memory: 8.38 GB / 12.32 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Yarn: 1.22.15
    npm: 8.3.1
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.17 
    @sveltejs/kit: next => 1.0.0-next.260 
    svelte: ^3.44.0 => 3.46.4

Severity

blocking an upgrade

Additional Information

I assume this is because in load_node we are only looking at shadow.status when shadow.error or shadow.redirect are set. We should also look at shadow.status when the page has no load function (whether or not we have shadow.body).

I'm not sure about whether we want to use shadow.status if there's a mod.load and it doesn't return its own status.

[Conduitry]

This was resolved by #4328.