The agent emits `MEDIA:<path>` to signal file delivery to the gateway,
and `[[audio_as_voice]]` as a voice-delivery hint. The gateway strips
both before sending to Telegram/Discord/Slack, but the TUI was rendering
them raw through markdown — which is also how the intraword underscore
bug originally surfaced (`browser_screenshot_ecc…`).
At the `Md` layer, detect both sentinels on their own line:
- `MEDIA:<path>` → `▸ <path>` with the path rendered literal and wrapped
in a `Link` for OSC 8 hyperlink support (absolute paths get a
`file://` URL, so modern terminals make them click-to-open).
- `[[audio_as_voice]]` → dropped silently; it has no meaning in TUI.
Covers tests for quoted/backticked MEDIA variants, Windows drive paths,
whitespace, and the inline-in-prose case (left untouched — still
protected by the intraword-underscore guard).