Apply wp-ai-client connect timeout to cURL

[chubes4]

Summary

• Applies Data Machine's resolved wp-ai-client connect timeout to WordPress HTTP's cURL handle via CURLOPT_CONNECTTIMEOUT.
• Keeps the existing low-speed timeout behavior unchanged.
• Extends the wp-ai-client timeout smoke test to assert that the cURL hook receives both request and connect timeouts.

Why

PR #1796 added a connect-timeout setting/filter and propagated request options through the model and prompt builder. Local validation then showed WordPress core's WP_AI_Client_HTTP_Client maps only total timeout from RequestOptions into WP HTTP args, so the actual cURL connect timeout still needed to be applied through Data Machine's scoped http_api_curl hook.

Testing

• php tests/wp-ai-client-request-timeout-smoke.php — 25 assertions
• php -l inc/Engine/AI/RequestBuilder.php && php -l tests/wp-ai-client-request-timeout-smoke.php
• git diff --check origin/main...HEAD

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafting the follow-up patch, smoke assertion updates, and PR description; Chris remains responsible for review and testing.