Add a common way to create HTTP client (#3110)

Ensure User-Agent and originator are always sent.

codex-rs/chatgpt/src/apply_command.rs

@@ -31,7 +31,7 @@ pub async fn run_apply_command(
         ConfigOverrides::default(),
     )?;
 
-    init_chatgpt_token_from_auth(&config.codex_home).await?;
+    init_chatgpt_token_from_auth(&config.codex_home, &config.responses_originator_header).await?;
 
     let task_response = get_task(&config, apply_cli.task_id).await?;
     apply_diff_from_task(task_response, cwd).await