test(qqbot): update voice detection tests for content_type-only logic

Update TestIsVoiceContentType to match the new behavior:
- Empty content_type with audio extensions → False (no sniffing)
- File upload with audio extension → False
- Added test_file_upload_with_audio_extension for the reported bug case

tests/gateway/test_qqbot.py

@@ -139,14 +139,21 @@ class TestIsVoiceContentType:
     def test_audio_content_type(self):
         assert self._fn("audio/mp3", "file.mp3") is True
 
-    def test_voice_extension(self):
-        assert self._fn("", "file.silk") is True
+    def test_voice_extension_ignored_when_content_type_empty(self):
+        """content_type='' with audio extension → False (no extension sniffing)."""
+        assert self._fn("", "file.silk") is False
 
     def test_non_voice(self):
         assert self._fn("image/jpeg", "photo.jpg") is False
 
-    def test_audio_extension_amr(self):
-        assert self._fn("", "recording.amr") is True
+    def test_audio_extension_amr_ignored_when_content_type_empty(self):
+        """content_type='' with .amr extension → False (no extension sniffing)."""
+        assert self._fn("", "recording.amr") is False
+
+    def test_file_upload_with_audio_extension(self):
+        """File upload with audio extension must NOT be treated as voice."""
+        assert self._fn("file", "song.mp3") is False
+        assert self._fn("file", "audio-30251.instrumental..wav") is False
 
 
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