style: improve string formatting in visualization functions

Author: MartinEBravo

src/agents/extensions/visualization.py

@@ -44,21 +44,21 @@ def get_all_nodes(agent: Agent, parent: Agent = None) -> str:
     if not parent:
         parts.append(
             f'"{agent.name}" [label="{agent.name}", shape=box, style=filled, '
-            'fillcolor=lightyellow, width=1.5, height=0.8];'
+            "fillcolor=lightyellow, width=1.5, height=0.8];"
         )
 
     # Smaller tools (ellipse, green)
     for tool in agent.tools:
         parts.append(
             f'"{tool.name}" [label="{tool.name}", shape=ellipse, style=filled, '
-            f'fillcolor=lightgreen, width=0.5, height=0.3];'
+            f"fillcolor=lightgreen, width=0.5, height=0.3];"
         )
 
     # Bigger handoffs (rounded box, yellow)
     for handoff in agent.handoffs:
         parts.append(
             f'"{handoff.name}" [label="{handoff.name}", shape=box, style=filled, style=rounded, '
-            f'fillcolor=lightyellow, width=1.5, height=0.8];'
+            f"fillcolor=lightyellow, width=1.5, height=0.8];"
         )
         parts.append(get_all_nodes(handoff))