The base media dispatch calls send_voice(..., is_voice=is_voice) for every
audio MEDIA attachment (gateway/platforms/base.py _send_one). MatrixAdapter
.send_voice() accepted neither is_voice nor **kwargs, so every non-image
MEDIA delivery raised TypeError and the file was silently dropped — the
failure is visible in rotated logs since 2026-09-08 (never worked).
Accept the flag explicitly: is_voice=False -> plain m.audio in the original
format (no transcode); True or omitted (play_audio legacy callers) -> the
existing MSC3245 voice-bubble path with best-effort Ogg/Opus transcode.
Fixes#116776
(cherry picked from commit d4f89a725498e29a2ee0fe016f8bb98db08f358c)
b6505448f1