fix(P0): Add function invoking marker and improve ChatMessage extraction

Changes:
1. Add __function_invoking_chat_client__ marker to HuggingFaceChatClient
- Without this marker, agent_framework ignores tools passed to the client
- The warning "does not support function invoking" is now eliminated

2. Improve _extract_text in AdvancedOrchestrator:
- Handle ChatMessage.contents (list of FunctionCallContent, TextContent)
- Extract tool call names when text content is empty
- Return empty string instead of object repr for graceful fallback

3. Fix WorkflowOutputEvent handling:
- Use _extract_text instead of str() to avoid object repr in output
- Provide meaningful fallback message when no text available

These fixes ensure the HuggingFace Free Tier can properly:
- Declare function calling capability to the framework
- Display tool calls and text content in events
- Show clean output instead of <ChatMessage object at ...>

src/clients/huggingface.py

@@ -29,6 +29,10 @@ logger = structlog.get_logger()
 class HuggingFaceChatClient(BaseChatClient):  # type: ignore[misc]
     """Adapter for HuggingFace Inference API with full function calling support."""
 
+    # Marker to tell agent_framework that this client supports function calling
+    # Without this, the framework warns and ignores tools
+    __function_invoking_chat_client__ = True
+
     def __init__(
         self,
         model_id: str | None = None,

src/orchestrators/advanced.py

@@ -337,32 +337,44 @@ The final output should be a structured research report."""
         """
         Defensively extract text from a message object.
 
-        Fixes bug where message.text might return the object itself or its repr.
+        Handles ChatMessage objects from both OpenAI and HuggingFace clients.
+        ChatMessage has: .text (str), .contents (list of content objects)
         """
         if not message:
             return ""
 
-        # Priority 1: .content (often the raw string or list of content)
+        # Priority 1: .text (standard ChatMessage text content)
+        if hasattr(message, "text") and message.text:
+            text = message.text
+            # Verify it's actually a string, not the object itself
+            if isinstance(text, str) and not (text.startswith("<") and "object at" in text):
+                return text
+
+        # Priority 2: .contents (list of FunctionCallContent, TextContent, etc.)
+        # This handles tool call responses from HuggingFace
+        if hasattr(message, "contents") and message.contents:
+            parts = []
+            for content in message.contents:
+                # TextContent has .text
+                if hasattr(content, "text") and content.text:
+                    parts.append(str(content.text))
+                # FunctionCallContent has .name and .arguments
+                elif hasattr(content, "name"):
+                    parts.append(f"[Tool: {content.name}]")
+            if parts:
+                return " ".join(parts)
+
+        # Priority 3: .content (legacy - some frameworks use singular)
         if hasattr(message, "content") and message.content:
             content = message.content
-            # If it's a list (e.g., Multi-modal), join text parts
+            if isinstance(content, str):
+                return content
             if isinstance(content, list):
                 return " ".join([str(c.text) for c in content if hasattr(c, "text")])
-            return str(content)
-
-        # Priority 2: .text (standard, but sometimes buggy/missing)
-        if hasattr(message, "text") and message.text:
-            # Verify it's not the object itself or a repr string
-            text = str(message.text)
-            if text.startswith("<") and "object at" in text:
-                # Likely a repr string, ignore if possible
-                pass
-            else:
-                return text
 
-        # Fallback: If we can't find clean text, return str(message)
-        # taking care to avoid infinite recursion if str() calls .text
-        return str(message)
+        # Fallback: Return empty string instead of repr
+        # The repr is useless for display purposes
+        return ""
 
     def _get_event_type_for_agent(self, agent_name: str) -> str:
         """Map agent name to appropriate event type.
@@ -456,9 +468,11 @@ The final output should be a structured research report."""
 
         elif isinstance(event, WorkflowOutputEvent):
             if event.data:
+                # Use _extract_text to properly handle ChatMessage objects
+                text = self._extract_text(event.data)
                 return AgentEvent(
                     type="complete",
-                    message=str(event.data),
+                    message=text if text else "Research complete (no synthesis)",
                     iteration=iteration,
                 )