[FEATURE]: Render agent-generated audio files inline in Desktop

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Could it be possible for OpenCode Desktop to render an audio recording created by an agent directly in the session timeline?

When an agent creates or links a local .mp3 or .wav file, OpenCode currently leaves the user to open it in another application. A compact inline player—with play/pause, seeking, duration, filename, and an external-open action—would make the output immediately reviewable. It should not autoplay, and it can fall back to the normal file link when the file is missing or unsupported.

The smallest useful scope is Desktop support for local MP3 and WAV outputs referenced by an assistant message. This is only output rendering: no microphone input, speech-to-text, TTS generation, or provider-side audio support.

Codex Desktop provides the target interaction: a recording returned in a response can be played inline.

I checked the nearby requests: #22260 is about sending audio/video into models, and #26940 is about voice input/TTS. Neither covers playing an audio artifact the agent already produced.

Codex rendering example

Codex renders a linked recording as an inline player when the response uses image-style Markdown with an audio file path:

![audio](</absolute/path/to/recording.mp3>)

The angle brackets keep paths containing spaces valid. The requested behavior is the resulting in-app player, not the exact Markdown syntax.