[fsapp] turn-end exit_reason can finalize a queued task before display queue done

[Tomodad]

Summary

_make_task_hook in frontends/fsapp.py currently treats a turn-level exit_reason as completion of the whole Feishu task and calls the task's on_final callback immediately.

That callback is _finish, which sets result["sent"] = True. As a result, run_agent can leave its display-queue loop before the queue publishes its real {"done": ...} item. The card may therefore be marked complete from an intermediate turn response, and final generated-file/attachment handling can run with the wrong text instead of the completed task result.

This is also observable when a single hook context contains both exit_reason and summary/tool_calls: the exit_reason branch wins, so the step is not added to the task card.

Reproduction

Tested against lsdefine/GenericAgent@172889fcb00fc735c67a7969edcb6767cc2bb9f9 with an isolated harness that AST-loads _make_task_hook and its formatting helpers.

[01_exit_reason_with_response_triggers_on_final]
expect={'on_final': 1, 'step': 0, 'fail': 0}
actual={'on_final': 1, 'step': 0, 'fail': 0}

[05_summary_and_exit_reason_together_exit_reason_wins]
expect={'on_final': 1, 'step': 0, 'fail': 0}
actual={'on_final': 1, 'step': 0, 'fail': 0}
on_final_arg='final text'

The second case demonstrates that summary="wrote file" is discarded when exit_reason="end_turn" is present in the same context.

Expected behavior

A turn-end hook should update per-turn card steps when a summary is available, but it should not declare the entire queued task complete. Task completion should wait for the display queue's real done item; timeout, stop, and exception paths should remain failures rather than successful finalization.

Actual behavior

Any matching hook context with a truthy exit_reason calls _finish early. This can mark the card complete and set result["sent"] before the display queue is done.

A follow-up PR will keep the change limited to this false-terminal behavior.