fix: detect and prevent redirect loops with Client/Pool

[mcollina]

Summary

Fixes redirect interceptor failing to redirect with Client and Pool by detecting redirect loops that occur when single-host dispatchers attempt cross-origin redirects.

Problem

Issue #4360 reported that when using Client or Pool with the redirect interceptor, cross-origin redirects would fail silently and loop infinitely instead of following the redirect properly. This happened because:

1. Client and Pool are single-host dispatchers bound to specific origins
2. They cannot handle cross-origin redirects properly
3. Instead of failing cleanly, they would loop trying to redirect to the same URL repeatedly

Solution

• Added redirect loop detection in RedirectHandler
• When a redirect loop is detected, throw a clear error message instead of infinite looping
• The error message guides users to use Agent for cross-origin redirects
• Agent continues to work correctly for cross-origin redirects

Test Plan

• Added comprehensive tests covering Client, Pool, and Agent behavior
• ✅ Client throws clear error for cross-origin redirects
• ✅ Pool throws clear error for cross-origin redirects
• ✅ Agent successfully follows cross-origin redirects
• ✅ Same-origin redirects continue to work with Agent

Error Message

Before: Silent infinite loops until maxRedirections reached
After: Redirect loop detected. Cannot redirect to ${origin}. This typically happens when using a Client or Pool with cross-origin redirects. Use an Agent for cross-origin redirects.

Fixes #4360

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