fix(whatsapp): skip reply prefix in bot mode — only needed for self-chat (#3931)

The WhatsApp bridge prepends '⚕ *Hermes Agent*\n────────────\n' to
every outgoing message. In self-chat mode this is necessary to
distinguish the bot's responses from the user's own messages. In bot
mode the messages already come from a different number, making the
prefix redundant and cluttered.

Now only prepends the prefix when WHATSAPP_MODE is 'self-chat' (the
default). Bot mode messages are sent clean.

scripts/whatsapp-bridge/bridge.js

@@ -55,6 +55,10 @@ const REPLY_PREFIX = process.env.WHATSAPP_REPLY_PREFIX === undefined
   : process.env.WHATSAPP_REPLY_PREFIX.replace(/\\n/g, '\n');
 
 function formatOutgoingMessage(message) {
+  // In bot mode, messages come from a different number so the prefix is
+  // redundant — the sender identity is already clear.  Only prepend in
+  // self-chat mode where bot and user share the same number.
+  if (WHATSAPP_MODE !== 'self-chat') return message;
   return REPLY_PREFIX ? `${REPLY_PREFIX}${message}` : message;
 }