fix: don't emit the unused bundle and stylesheet files when using bundleStrategy: 'inline'

[Nic-Polumeyv]

With bundleStrategy: 'inline', the bundle and stylesheet are written to _app/immutable even though their content is inlined into the page, so the build ships a full copy of the app that nothing ever loads. In the default template that roughly doubles the output size, and a service worker will happily precache the dead files too.

This deletes both files (and the bundle sourcemap if present) once their content has been captured for inlining, and filters anything that no longer exists out of the $service-worker build list. version.json stays, since the version checker can still fetch it at runtime. Of the unused files listed in the issue, env.js no longer reproduces on current main, so these two were the ones left. I went with deleting the files after the build rather than suppressing their emission inside it, since find_deps and the manifest plumbing still need the entries to exist, but open to a different route if preferred.

The options-3 app now has a service worker and a stylesheet, and its build-mode tests assert the inlined files are gone from _app/immutable (including sourcemaps), the service worker build list is clean, and version.json survives. The emitted-files assertions fail on main.

Found this one while working on #16024 and digging through how the client build decides what to emit.

Fixes #13700

---

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

Edits

• Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2852496

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	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[teemingc]

We ought to avoid creating a new test app for this and instead reuse the one at packages/kit/test/apps/options-3 which is already configured to inline the app.

[teemingc]

Thanks!