fix: normalize Windows path casing in config warning

[LogicDX342]

Fixes false positive Vite config override warnings on Windows when SvelteKit compares equivalent filesystem paths with different casing.

SvelteKit already normalizes path separators before comparing enforced Vite config values. However, on Windows, path casing can also differ between the incoming config and resolved config, for example e:/... vs E:/.... Those paths refer to the same filesystem location, but the current string comparison can still report an override warning such as:

The following Vite config options will be overridden by SvelteKit:
  - root

This PR normalizes casing on Windows for enforced config values that are filesystem paths.

Related issue: #16293

---

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.

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 7689adc:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/7689adc00e515a87c0b22338045ce3b85362b952

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16239

Note

This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 7689adc

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

Accidental approval; need to discuss on Thursday

[teemingc]

See #16293 (comment)