Replace HttpClient php-curl-class transport with native curl adapters

Summary

Follow up the HttpClient adapter/factory refactor by replacing the php-curl-class/php-curl-class transport behind Quantum-owned adapters with native curl implementations, while preserving the public HttpClient facade, factory methods, helpers, and adapter contracts introduced in the previous work.

This is an umbrella ticket. The implementation should be split into adapter-specific child tickets so the simpler single-request adapter can be validated separately from the higher-risk multi-request behavior.

Goals

• Keep the public HttpClient API stable.
• Keep HttpClientFactory and helper APIs stable:
  • HttpClientFactory::createRequest() / httpRequest()
  • HttpClientFactory::createMultiRequest() / httpMultiRequest()
  • HttpClientFactory::createAsyncMultiRequest() / httpAsyncMultiRequest()
• Replace vendor-backed internals adapter by adapter.
• Remove php-curl-class/php-curl-class only after both native adapters have acceptable parity.
• Avoid leaking raw native curl handles through the public facade.

Child Tickets

• Native CurlAdapter implementation for single requests.
• Native MultiCurlAdapter implementation for multi and async requests.

Acceptance Criteria

• Child tickets are completed and validated independently.
• Existing HttpClient unit tests continue to pass.
• Downstream single-request usage such as remote image downloads continues to work.
• Multi-request callback behavior is covered before removing the dependency.
• php-curl-class/php-curl-class is removed from Composer only after native single and multi adapters are both complete, reviewed, and validated.

Notes

The multi-curl adapter is the risky part because queueing, callbacks, request IDs, headers, cookies, options, errors, and response aggregation all need behavior parity. Do not treat dependency removal as complete after only the single-request adapter is native.

Start by reading the existing HttpClient adapter and factory refactor, including the HttpClientFactory entry points and existing HttpClient unit tests. Treat the single-request and multi/async adapters as separate child tickets; done means stable public APIs, validated request and callback behavior, and removal of php-curl-class only after both adapters pass parity checks.