Feedback-Loop buttons and Generated-by-AI label not showing when ending a streaming

Description

The feedback buttons and AI-Generated label are not shown in a streaming message even when context.streaming_response.set_feedback_loop(True) and context.streaming_response.set_generated_by_ai_label(True) are set.

There are two bugs causing this issue:

1. Feedback metadata remains contradictory

In StreamingResponse._send_activity(), setting both the feedback loop and its type enters this branch:

if self._enable_feedback_loop and self._feedback_loop_type:
    streaminfo_entity.feedback_loop = {"type": self._feedback_loop_type}
else:
    streaminfo_entity.feedback_loop_enabled = self._enable_feedback_loop

Because the else is skipped, feedback_loop_enabled retains the StreamInfo default of False, producing:

{
  "feedbackLoop": {
    "type": "default"
  },
  "feedbackLoopEnabled": false
}

2. AI metadata requires citations

Activity.add_ai_metadata() currently wraps the entire operation in:

if citations:

Consequently, it never adds an AIEntity when the message has no citations—even when set_generated_by_ai_label(True) and a sensitivity label are configured.