feat(api): prioritize auth args over env vars

Author: axl1313

src/codex/_client.py

@@ -101,14 +101,14 @@ def __init__(
         - `api_key` from `CODEX_API_KEY`
         - `access_key` from `CODEX_ACCESS_KEY`
         """
-        if api_key is None:
-            api_key = os.environ.get("CODEX_API_KEY")
         self.api_key = api_key
-
-        if access_key is None:
-            access_key = os.environ.get("CODEX_ACCESS_KEY")
         self.access_key = access_key
 
+        # if neither api_key nor access_key are provided, check the environment variables
+        if self.api_key is None and self.access_key is None:
+            self.api_key = os.environ.get("CODEX_API_KEY")
+            self.access_key = os.environ.get("CODEX_ACCESS_KEY")
+
         self._environment = environment
 
         base_url_env = os.environ.get("CODEX_BASE_URL")