The inline markdown regex had `~([^~\s][^~]*?)~` for Pandoc-style subscript
(H~2~O, CO~2~). On models that decorate prose with kaomoji like `thing ~!`
and `cool ~?` — Kimi especially — the opener `~!` paired with the next
stray `~` on the line and dim-formatted everything between them with a
leading `_` character, mangling markdown output.
Tighten the pattern to short alphanumeric-only content (`~[A-Za-z0-9]{1,8}~`)
since real subscript never contains punctuation, spaces, or long runs.
Same tightening applied to stripInlineMarkup so width measurement stays
consistent. Classic CLI was unaffected because it renders these literally.
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).
