fix: normalize static file cache paths on Windows

[ikxin]

Summary

Fixes static asset serving in vinext start on Windows by normalizing StaticFileCache lookup keys to URL-style forward slashes.

On Windows, path.relative(base, file) returns paths with \ separators. StaticFileCache currently stores those paths directly as lookup keys, producing entries such as:

/_next\static\index-C5wrhk-x.css
/images\logo.svg

Browsers request URL paths with / separators:

/_next/static/index-C5wrhk-x.css
/images/logo.svg

Because the cache key and request pathname do not match, valid files that exist under dist/client are returned as 404 by vinext start.

This patch converts scanned relative file paths to URL path separators before inserting them into the static cache.

Reproduction

On Windows:

1. Build an App Router project with static assets:

pnpm run build
pnpm exec vinext start

2. Open a built route in the browser.
3. Observe 404s for valid assets such as:

/_next/static/*.js
/_next/static/*.css
/images/logo.svg

The files exist on disk under dist/client, but the production server cannot serve them because the in-memory static cache uses backslash-separated keys.

Fix

Normalize the relative path generated during static file scanning:

path.relative(base, file).replaceAll(path.sep, "/")

This keeps behavior unchanged on POSIX platforms and makes Windows cache keys match URL pathnames.

Verification

Verified in a Windows project using vinext@0.0.52:

• pnpm run build succeeds.
• vinext start serves the app route successfully.
• Actual HTML-referenced assets under /_next/static/* return 200.
• Public assets such as /images/logo.svg return 200.
• Browser console no longer reports static asset 404s.

Related

Related to #1337 in that both involve _next/static 404 handling, but this PR fixes a different root cause: valid static assets on Windows are cached under backslash-separated keys.

Similar class of Windows path normalization issue as #825.

[Copilot]

Pull request overview

This pull request fixes static asset serving on Windows in vinext start by ensuring StaticFileCache uses URL-style (/) path separators for its lookup keys, matching browser request pathnames.

Changes:

• Normalize path.relative(base, file) results to forward-slash URL paths before inserting into the static file cache.

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