[Website] Fix Safari PWA cache failures by stripping Range headers

[adamziel]

Summary

This is a potential fix for intermittent Safari PWA failures after deployments where the site displays a blank page until the cache is manually cleared.

Theory: Safari sometimes adds Range headers to asset requests, causing servers to return 206 Partial Content responses. These partial responses fail when using Cache.put() because the Cache API requires complete responses.

The Problem

After deploying playground.wordpress.net, Safari users sometimes experience:

• Blank page on reload, even though assets like main.js are accessible
• The files exist and load fine in new tabs
• Only clearing the cache and reloading fixes it
• Chrome and Firefox work fine with the same network-first caching strategy

The Fix

Strip the Range header from requests before fetching in cacheFirstFetch(). This ensures:

• Servers return 200 OK with complete responses instead of 206 Partial Content
• Responses can be successfully cached with Cache.put()
• Consistent behavior across all browsers

Important Note

This is a best-guess fix since the issue is not easily reproducible outside the deployed production environment. The Safari-specific behavior with Range headers in PWA contexts is well-documented, and this fix addresses that known issue. However, the root cause of the blank page problem may be more complex.

Testing

The change is defensive and shouldn't affect normal operation:

• If no Range header is present, the request passes through unchanged
• If a Range header exists, a new request is created without it
• All other headers and request properties are preserved