fix(tui): render MEDIA: as a clickable file chip, drop audio directive

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).

ui-tui/src/components/markdown.tsx

@@ -12,6 +12,9 @@ const DEF_RE = /^\s*:\s+(.+)$/
 const TABLE_DIVIDER_CELL_RE = /^:?-{3,}:?$/
 const MD_URL_RE = '((?:[^\\s()]|\\([^\\s()]*\\))+?)'
 
+export const MEDIA_LINE_RE = /^\s*[`"']?MEDIA:\s*(\S+?)[`"']?\s*$/
+export const AUDIO_DIRECTIVE_RE = /^\s*\[\[audio_as_voice\]\]\s*$/
+
 export const INLINE_RE = new RegExp(
   `(!\\[(.*?)\\]\\(${MD_URL_RE}\\)|\\[(.+?)\\]\\(${MD_URL_RE}\\)|<((?:https?:\\/\\/|mailto:)[^>\\s]+|[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,})>|~~(.+?)~~|\`([^\\\`]+)\`|\\*\\*(.+?)\\*\\*|(?<!\\w)__(.+?)__(?!\\w)|\\*(.+?)\\*|(?<!\\w)_(.+?)_(?!\\w)|==(.+?)==|\\[\\^([^\\]]+)\\]|\\^([^^\\s][^^]*?)\\^|~([^~\\s][^~]*?)~|(https?:\\/\\/[^\\s<]+))`,
   'g'
@@ -267,6 +270,35 @@ function MdImpl({ compact, t, text }: MdProps) {
         continue
       }
 
+      if (AUDIO_DIRECTIVE_RE.test(line)) {
+        i++
+
+        continue
+      }
+
+      const media = line.match(MEDIA_LINE_RE)
+
+      if (media) {
+        start('paragraph')
+
+        const path = media[1]!
+        const url = /^(?:\/|[a-z]:[\\/])/i.test(path) ? `file://${path}` : path
+
+        nodes.push(
+          <Text color={t.color.dim} key={key}>
+            {'▸ '}
+            <Link url={url}>
+              <Text color={t.color.amber} underline>
+                {path}
+              </Text>
+            </Link>
+          </Text>
+        )
+        i++
+
+        continue
+      }
+
       const fence = parseFence(line)
 
       if (fence) {