Add auto create session

Reviewed-on: #5

src/va_agent/agent.py

@@ -26,4 +26,9 @@ session_service = FirestoreSessionService(
     genai_client=genai.Client(),
 )
 
-runner = Runner(app_name="va_agent", agent=agent, session_service=session_service)
+runner = Runner(
+    app_name="va_agent",
+    agent=agent,
+    session_service=session_service,
+    auto_create_session=True,
+)

src/va_agent/server.py

@@ -66,13 +66,10 @@ def _build_user_message(request: QueryRequest) -> str:
     if request.type == "notification" and request.notification:
         parts = [request.text]
         if request.notification.text:
-            parts.append(
-                f"\n[Notificación recibida]: {request.notification.text}"
-            )
+            parts.append(f"\n[Notificación recibida]: {request.notification.text}")
         if request.notification.parameters:
             formatted = ", ".join(
-                f"{k}: {v}"
-                for k, v in request.notification.parameters.items()
+                f"{k}: {v}" for k, v in request.notification.parameters.items()
             )
             parts.append(f"[Parámetros de notificación]: {formatted}")
         return "\n".join(parts)