Enhance skills tool to have an arg so it is more reliably called, and error handling in agent

- Updated the `skills_categories` function to include a `verbose` parameter, allowing users to request skill counts per category.
- Modified the `handle_skills_function_call` method to pass the `verbose` argument to `skills_categories`.
- Improved error handling in the `AIAgent` class by injecting a recovery message when invalid JSON arguments are detected, guiding users on how to correct their tool calls.
- Enhanced the `GatewayRunner` to return a user-friendly error message if the agent fails to generate a final response, improving overall user experience.

tools/skills_tool.py

@@ -349,7 +349,7 @@ def _load_category_description(category_dir: Path) -> Optional[str]:
         return None
 
 
-def skills_categories(task_id: str = None) -> str:
+def skills_categories(verbose: bool = False, task_id: str = None) -> str:
     """
     List available skill categories with descriptions (progressive disclosure tier 0).
     
@@ -358,6 +358,7 @@ def skills_categories(task_id: str = None) -> str:
     or first paragraph to explain what skills are in that category.
     
     Args:
+        verbose: If True, include skill counts per category (default: False, but currently always included)
         task_id: Optional task identifier (unused, for API consistency)
         
     Returns: