fix: identify circular imports from src/env

[svelte-triage-bot]

Fixes #17013.

When src/env imports a dependency that imports $app/env/private or $app/env/public, loading the environment configuration depends on modules that have not yet been generated.

Recognize this resolution failure and report the circular dependency directly instead of exposing the internal generated-module path. When available, the diagnostic now identifies the project-relative module that imported $app/env/private or $app/env/public.

A regression test covers the transitive helper-import pattern and verifies that the responsible helper module is reported.

Testing

• pnpm vitest run -c vitest.kit.config.js src/core/sync/sync.spec.js --reporter=verbose
• pnpm -F @sveltejs/kit test:unit
• pnpm format
• pnpm -F @sveltejs/kit lint
• pnpm -F @sveltejs/kit prepublishOnly

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 2c90fd5:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/2c90fd575e104fd3c4be91756495774e8585d906

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/17014

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: 2c90fd5

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

[ottomated]

@svelte-triage-bot Throw the error using stackless so it doesn't take up so much space in the terminal

[svelte-triage-bot]

Implemented and pushed the stackless change to the existing PR branch.

• Commit: 2c90fd575e104fd3c4be91756495774e8585d906
• Updated regression test verifies the diagnostic has no stack.
• Focused tests, unit tests, formatting, lint, and prepublish checks pass.

I also recorded this feedback in svelte-agent#5.