Fix controlled-failure crash in run skill

The run skill raised RuntimeError for scenario=controlled-failure,
causing HTTP500. Return the safe recovered result instead and add
regression coverage.

agent.py

@@ -23,7 +23,7 @@ class SelfHealingDemo(A2AAgent):
         scenario: str = "normal",
     ) -> dict[str, object]:
         if scenario == "controlled-failure":
-            # Intentional smoke fixture: the regression test specifies the safe
-            # result. The production self-healing worker must repair this source.
-            raise RuntimeError("SELF_HEAL_SMOKE: controlled invoice total handler crashed")
+            # Previously this handler crashed with a controlled RuntimeError.
+            # It now returns the safe, recovered result the regression test expects.
+            return {"ok": True, "scenario": scenario, "result": "recovered"}
         return {"ok": True, "scenario": scenario, "result": "healthy"}