feat(agent): mark and propagate voice input metadata in agent messages; clarify terminal tool usage in prompts

- Add `has_audio_input` flag to agent message handling and propagate through processing pipeline
- Structure agent input payloads to include `input.mode` and `input.transcribed` for voice messages
- Update prompts and tool descriptions to clarify that `send_voice_message` and `ask_user_choice` are terminal tools and should not be followed by redundant text replies
- Enhance tests to cover voice input metadata propagation and prompt updates

tests/test_agent_prompt_style.py

@@ -244,6 +244,24 @@ class TestAgentPromptStyle(unittest.TestCase):
             prompt,
         )
 
+    def test_voice_prompt_marks_voice_tool_as_terminal_reply(self):
+        """语音回复提示词应说明语音工具会结束当前轮次。"""
+        with patch.object(settings, "LLM_SUPPORT_AUDIO_OUTPUT", True):
+            prompt = prompt_manager.get_agent_prompt()
+
+        self.assertIn("send_voice_message", prompt)
+        self.assertIn("terminal response tool", prompt)
+        self.assertIn("do not write a final text reply after it", prompt)
+        self.assertIn("text fallback and still completes the reply", prompt)
+
+    def test_core_prompt_describes_voice_input_metadata(self):
+        """核心提示词应说明结构化消息中的语音输入元信息。"""
+        prompt = prompt_manager.get_agent_prompt()
+
+        self.assertIn("input.mode", prompt)
+        self.assertIn("voice", prompt)
+        self.assertIn("`message` contains its transcript", prompt)
+
     def test_verbose_prompt_does_not_inject_silence_until_tools_finish_rule(self):
         with patch.object(settings, "AI_AGENT_VERBOSE", True):
             prompt = prompt_manager.get_agent_prompt()