Switch to Granite 4.0 Micro and fix import errors

- Updated model from granite-3.1-8b-instruct to granite-4.0-micro
- Added missing get_mcp_registry() function to mcp/registry.py
- Updated all documentation to reflect Granite 4.0 Micro
- Updated performance metrics for the more efficient model

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

mcp/registry.py

@@ -236,3 +236,24 @@ class MCPRegistry:
     def get_summary_service(self):
         """Get summary service (only available in in-memory mode)"""
         return getattr(self, 'summary', None)
+
+
+# Global registry instance
+_registry_instance = None
+
+def get_mcp_registry(use_in_memory: bool = None) -> MCPRegistry:
+    """
+    Get or create the global MCP registry instance.
+
+    Args:
+        use_in_memory: If True, use in-memory services. If None, use env var.
+
+    Returns:
+        MCPRegistry instance
+    """
+    global _registry_instance
+
+    if _registry_instance is None:
+        _registry_instance = MCPRegistry(use_in_memory=use_in_memory)
+
+    return _registry_instance