fix: preserve URL query params for Azure OpenAI and custom endpoints

Azure OpenAI requires an `api-version` query parameter on every request.
When users include it in the base_url (e.g. `?api-version=2025-04-01-preview`),
the OpenAI SDK silently drops it during URL construction, causing 404 errors.

Extract query params from base_url and pass them via `default_query` so the
SDK appends them to every request. This is a generic solution that works for
any custom endpoint requiring query parameters, not just Azure.

No-op for URLs without query params — fully backward compatible.

run_agent.py

@@ -40,6 +40,7 @@ from types import SimpleNamespace
 import urllib.request
 import uuid
 from typing import List, Dict, Any, Optional
+from urllib.parse import urlparse, parse_qs, urlunparse
 from openai import OpenAI
 import fire
 from datetime import datetime
@@ -1314,7 +1315,22 @@ class AIAgent:
             if api_key and base_url:
                 # Explicit credentials from CLI/gateway — construct directly.
                 # The runtime provider resolver already handled auth for us.
-                client_kwargs = {"api_key": api_key, "base_url": base_url}
+                # Extract query params (e.g. Azure api-version) from base_url
+                # and pass via default_query to prevent loss during SDK URL
+                # joining (httpx drops query string when joining paths).
+                _parsed_url = urlparse(base_url)
+                if _parsed_url.query:
+                    _clean_url = urlunparse(_parsed_url._replace(query=""))
+                    _query_params = {
+                        k: v[0] for k, v in parse_qs(_parsed_url.query).items()
+                    }
+                    client_kwargs = {
+                        "api_key": api_key,
+                        "base_url": _clean_url,
+                        "default_query": _query_params,
+                    }
+                else:
+                    client_kwargs = {"api_key": api_key, "base_url": base_url}
                 if _provider_timeout is not None:
                     client_kwargs["timeout"] = _provider_timeout
                 if self.provider == "copilot-acp":