Fix request pipeline, authentication, cancellation, and URL handling

[ANSCoder]

Summary

• Retry HTTP 429 and 5xx responses; restrict built-in retries to idempotent methods and cap backoff and total retries.
• Honor endpoint auth overrides, prevent auth-provider refresh recursion, and strip common credentials and cookies from explicit no-auth requests.
• Preserve query strings when resolving relative URLs.
• Propagate cancellation through retries and decoding; move JSON and image decoding off actors and limit image prefetch concurrency.
• Redact query values, URL user info, and fragments from request logs.
• Add pipeline regression tests and update the README, changelog, and example documentation.

Compatibility

Public Swift signatures remain source-compatible, but request behavior changes. Recommend releasing as 2.0.0.

Testing

• git diff --check passes.
• Tests were not run.

[github-actions]

	Warnings
⚠️	PR is large (987 lines). Consider splitting.

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