fix(miniflare): bypass proxy for local inspector connections

[Zuckjet]

Fixes #8906

When users have proxy environment variables set (HTTP_PROXY, HTTPS_PROXY, etc.), the local development server fails to start with a "TypeError: fetch failed" error.

Root cause

• Wrangler detects proxy environment variables and sets a global ProxyAgent
• Miniflare's InspectorProxyController makes a fetch request to 127.0.0.1 to connect to the workerd inspector
• This local request incorrectly goes through the proxy, which typically cannot handle localhost addresses, causing the connection to fail

Solution

Modified InspectorProxyController.updateConnection() to use a dedicated Agent for the local fetch request, bypassing the global proxy settings. Local inspector connections should never be proxied.

---

• Tests
  • [ ] Tests included/updated
  • [x] Tests not necessary because: Tested locally with proxy environment variables set
• Public documentation
  • [ ] Cloudflare docs PR(s):
  • [x] Documentation not necessary because: This should be defalut behavior
• Wrangler V3 Backport
  • [ ] Wrangler PR:
  • [x] Not necessary because: Not a patch change, not a Wrangler change

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Latest commit: cd09cfe9823b9a7f2d87bff80907b607c91ed95e

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