Prerendered root page with base path enabled is broken on Netlify

[teemingc]

Describe the bug

Having a base path and a prerendered root page deployed to Netlify causes the URL without a trailing slash /base-path to have broken CSS and JS links while the URL with a trailing slash /base-path/ returns the 404 page.

If the root page is not prerendered but we still have a base path, the URL without a trailing slash returns a 404 text response and the URL with a trailing slash successfully returns the root page.

I think the expected outcome is for the URL without a trailing slash to return the root page and the URL with a trailing slash to redirect to the URL without a trailing slash.

Reproduction

1. Prerender the root page src/routes/+page.svelte
2. Add a base path to svelte.config.js
3. Build and deploy to Netlify using the netlify adapter @sveltejs/adapter-netlify

Logs

No response

System Info

.

Severity

serious, but I can work around it

Additional Information

No response

[teemingc]

When a base path is set, the root page in builder.prerendered.paths ends with a trailing slash despite the description of the property saying that it doesn't:

kit/packages/kit/src/types/private.d.ts

Lines 189 to 190 in d512606

	/** An array of prerendered paths (without trailing slashes, regardless of the trailingSlash config) */
	paths: string[];

This causes the trailing slash path /base-path/ to be excluded from the edge manifest instead of the non-trailing slash path /base-path so it hits the edge function instead of our prerendered page?