Fix subagent auth: propagate parent API key to child agents

When using Nous Portal (or any non-OpenRouter provider), child agents
spawned by delegate_task failed with "No pricing available" or "Unknown
model" errors because they had no valid API key.

The delegate tool passed base_url but not api_key to child AIAgent
instances. Without an explicit key, children fell back to the empty
OPENROUTER_API_KEY env var, causing auth failures.

Extract the parent's API key from _client_kwargs and pass it through.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/delegate_tool.py

@@ -99,8 +99,14 @@ def _run_single_child(
     child_prompt = _build_child_system_prompt(goal, context)
 
     try:
+        # Extract parent's API key so subagents inherit auth (e.g. Nous Portal)
+        parent_api_key = None
+        if hasattr(parent_agent, '_client_kwargs'):
+            parent_api_key = parent_agent._client_kwargs.get("api_key")
+
         child = AIAgent(
             base_url=parent_agent.base_url,
+            api_key=parent_api_key,
             model=model or parent_agent.model,
             max_iterations=max_iterations,
             enabled_toolsets=child_toolsets,