Describe the bug

When submitting a form with CSR disabled (or in a browser with JS disabled), there doesn't seem to be a way to set the form values after submission.

With client side JS, we can use the enhance() functionality to keep form values after submission. As far as I can tell, there's no way of doing this serverside because the form.fields.set() function returns early after a submission.

I think this would be resolved by #14815, but I'm also curious what the rationale is for ignoring set() calls after submission?

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-f1jca1md?file=src%2Froutes%2F%2Bpage.svelte

Logs

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.0 => 7.0.1 
    @sveltejs/kit: ^2.48.5 => 2.53.4 
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.4 
    svelte: ^5.43.8 => 5.53.6 
    vite: ^7.2.2 => 7.3.1

Severity

blocking an upgrade

Additional Information

No response