hermes send "MEDIA:/x.png This Caption" now arrives as one native captioned
bubble instead of a separate text message followed by an uncaptioned bubble.
Root cause: the standalone senders (hermes send / cron / send_message tool)
stripped the MEDIA: tag, sent the remaining text as its own message, and
called the media send with no caption -- even though hermes send's help
advertises the captioned form and the bridges/adapters already support a
caption. Signal already captioned correctly.
- tools/send_message_tool.py: new _media_caption_split() chokepoint decides
caption-vs-separate-body (single captionable non-voice file within the
platform's message-length cap). Wired into the Telegram, WhatsApp and
Discord dispatch paths.
- Telegram/WhatsApp/Discord: when the single captioned file is missing, the
caption text is delivered as a plain message so it is never silently lost.
- Telegram caption send gets a MarkdownV2->plain parse fallback.
- Tests: _media_caption_split unit tests + per-platform caption tests
(ride, multi-file fallback, voice exclusion, over-limit fallback,
missing-file text fallback); updated the 3 tests that asserted the old
text-then-media split.
Closes the gap reported against #58911 (the MEDIA_CAPTION directive PR);
credit to @ferreiraesilva for surfacing the caption behavior.
