feat: add $app/manifest module

[Rich-Harris]

Part of #16159. This adds an $app/manifest module containing information about the app — it replaces the equivalents in $service-worker (so that we can delete that module).

It exports four things:

• immutable is an array of { path: string } objects representing the contents of _app/immutable (empty in dev)
• files is an array of { path: string } objects representing the contents of static
• prerendered is an array of { path: string } objects representing all the prerendered pages/endpoints in your app (empty in dev, and during prerendering)
• routes is an array of { id: string } objects representing the routes of your app

Paths are relative to base. In a service worker, you can do e.g. cache.add(path) as part of an offline strategy.

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[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 294a1fd:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/294a1fd1faa209f842b76f5933b31a2b78e55a6a

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16372

[changeset-bot]

🦋 Changeset detected

Latest commit: 294a1fd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Minor

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16372-svelte.vercel.app/

[Rich-Harris]

Renamed build to immutable and files to assets. Couple of wrinkles:

• immutable contains a non-immutable file, namely _app/manifest.js itself. Which is weird. I guess we could move it to assets, though that would also be weird, but perhaps less weird.
• immutable/asset path strings no longer have the leading / (and nor does the Asset type) which I think makes sense. But I'm not sure what makes most sense for prerendered path strings. You wouldn't use it with asset(...), you'd use it with resolve(...), if anything, and resolve does expect a leading slash.

I wonder if we actually need to remove the leading / from RouteId as well. I can see that making sense — when you use a route ID you're resolving against the base path, and resolve(anything, '/foo') should, by rights, equal /foo`. Slightly disruptive change but maybe for the best.

[Rich-Harris]

Actually you know what? This could be how we distinguish route IDs from pathnames in resolve. This makes way more sense to me:

// valid
resolve('path/to/somewhere');
resolve('/path/to/[location]', { location: 'somewhere' });

// invalid
resolve('/path/to/somewhere');
resolve('path/to/[location]', { location: 'somewhere' });

[Rich-Harris]

Should probably also rename Pathname to Path, since Pathname suggests url.pathname which this isn't. Also it aligns with the path properties in the manifest

[elliott-with-the-longest-name-on-github]

Random thought: Do we have tests asserting that hashes are stable?

[Rich-Harris]

sort of https://github.com/sveltejs/kit/pull/16324/files#diff-926464272ba6b30c9cdacb161fcca380c88e73bf9903fc0e2fbc0c035075f083