feat: emit FlowFailedEvent when a flow execution fails

A failed flow never emitted a terminal lifecycle event, so the
`flow_started` scope stayed open and consumers such as tracing closed the
root span with a generic orphaned message instead of the real error.
`kickoff_async` and the resume path now emit `FlowFailedEvent`, paired
with `flow_started` and carrying the exception, after draining pending
handlers and background memory writes. The resume path also emits the
`MethodExecutionStartedEvent` it was missing for the method being resumed,
so its finished or failed event pairs with its own scope instead of
popping the flow's.

docs/edge/ar/concepts/event-listener.mdx

@@ -157,6 +157,7 @@ class MyCustomCrew:
 - **FlowCreatedEvent**: يُرسل عند إنشاء تدفق
 - **FlowStartedEvent**: يُرسل عند بدء تنفيذ تدفق
 - **FlowFinishedEvent**: يُرسل عند اكتمال تنفيذ تدفق
+- **FlowFailedEvent**: يُرسل عند فشل تنفيذ تدفق. يحتوي على اسم التدفق والاستثناء الذي أنهى التنفيذ.
 - **FlowPausedEvent**: يُرسل عند إيقاف تدفق مؤقتًا بانتظار ملاحظات بشرية
 
 ### أحداث LLM

docs/edge/en/concepts/event-listener.mdx

@@ -256,6 +256,7 @@ CrewAI provides a wide range of events that you can listen for:
 - **FlowCreatedEvent**: Emitted when a Flow is created
 - **FlowStartedEvent**: Emitted when a Flow starts execution
 - **FlowFinishedEvent**: Emitted when a Flow completes execution
+- **FlowFailedEvent**: Emitted when a Flow execution fails. Contains the flow name and the exception that ended the execution.
 - **FlowPausedEvent**: Emitted when a Flow is paused waiting for human feedback. Contains the flow name, flow ID, method name, current state, message shown when requesting feedback, and optional list of possible outcomes for routing.
 - **FlowPlotEvent**: Emitted when a Flow is plotted
 - **MethodExecutionStartedEvent**: Emitted when a Flow method starts execution

docs/edge/ko/concepts/event-listener.mdx

@@ -255,6 +255,7 @@ CrewAI는 여러분이 청취할 수 있는 다양한 이벤트를 제공합니
 - **FlowCreatedEvent**: Flow가 생성될 때 발생
 - **FlowStartedEvent**: Flow가 실행을 시작할 때 발생
 - **FlowFinishedEvent**: Flow가 실행을 완료할 때 발생
+- **FlowFailedEvent**: Flow 실행이 실패할 때 발생합니다. Flow 이름과 실행을 종료시킨 예외를 포함합니다.
 - **FlowPausedEvent**: 사람의 피드백을 기다리며 Flow가 일시 중지될 때 발생합니다. Flow 이름, Flow ID, 메서드 이름, 현재 상태, 피드백 요청 시 표시되는 메시지, 라우팅을 위한 선택적 결과 목록을 포함합니다.
 - **FlowPlotEvent**: Flow가 플롯될 때 발생
 - **MethodExecutionStartedEvent**: Flow 메서드가 실행을 시작할 때 발생

docs/edge/pt-BR/concepts/event-listener.mdx

@@ -256,6 +256,7 @@ O CrewAI fornece uma ampla variedade de eventos para escuta:
 - **FlowCreatedEvent**: Emitido ao criar um Flow
 - **FlowStartedEvent**: Emitido ao iniciar a execução de um Flow
 - **FlowFinishedEvent**: Emitido ao concluir a execução de um Flow
+- **FlowFailedEvent**: Emitido quando a execução de um Flow falha. Contém o nome do flow e a exceção que encerrou a execução.
 - **FlowPausedEvent**: Emitido quando um Flow é pausado aguardando feedback humano. Contém o nome do flow, ID do flow, nome do método, estado atual, mensagem exibida ao solicitar feedback e lista opcional de resultados possíveis para roteamento.
 - **FlowPlotEvent**: Emitido ao plotar um Flow
 - **MethodExecutionStartedEvent**: Emitido ao iniciar a execução de um método do Flow