fix: serve_prerendered breaks on node http server

[gtm-nayan]

fixes #8888
Tests have been disabled for adapter-node since #2931, so didn't add any in this one. Will look into re-enabling.

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[dummdidumm]

Doesn't this need to be a regular dependency if we're using it in the code the user gets?

[gtm-nayan]

No, because it gets bundled.

[Rich-Harris]

oops! thanks for the fix. re tests — something i've been meaning to get round to for the longest time is:

• add realistic playwright tests that are part of the project template
• rig up test apps for each of the adapters that are rebuilt and deployed whenever Kit, the adapter, or the project template changes
• after each deploy, run the tests against the deployed URL

for adapter-node we could use render or fly or something