WhatsApp's Baileys library requires a separate mentions array in the
message payload for @mentions to work properly. Without this array,
text like '@5511999999999' appears as plain text instead of a clickable
mention.
This change automatically extracts phone numbers in the format
@<10-15 digits> from the message text AND media captions, adding them
to the mentions array as JIDs (e.g., '5511999999999@s.whatsapp.net').
Supported message types:
- Text messages
- Image with caption
- Video with caption
- Document with caption
Fixes mentions in group chats when using the message tool.
