feat(redirect): allow custom redirects to access response headers

[0x676e67]

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[Copilot]

Pull Request Overview

This PR adds the ability for custom redirect policies to access response headers from redirect attempts. The main purpose is to allow developers to make more informed decisions during redirects by examining headers such as cache-control, set-cookie, or custom headers from the redirect response.

• Added headers field to the Attempt struct in both redirect modules
• Updated all redirect policy interfaces to pass and expose headers
• Refactored code organization by moving helper functions and adding const qualifiers

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/redirect.rs	Added headers field to Attempt struct, updated Policy check method signature, and reorganized helper functions
src/client/layer/redirect/policy.rs	Added headers field and accessor method to policy Attempt struct
src/client/layer/redirect/future.rs	Updated Attempt construction to include response headers
examples/request_with_redirect.rs	Updated example to demonstrate accessing headers in custom redirect policy

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