hermes - 💡(How to fix) Fix feat: Add read-only / silent monitoring mode for WhatsApp adapter

Description

The WhatsApp adapter currently has a binary message flow:

• message is processed → agent sees it AND auto-replies
• message is filtered → agent doesn't see it at all

There's no way for messages to reach the agent's context (for monitoring/awareness) without the agent also responding automatically.

Proposed feature

A new configuration option like:

whatsapp:
  read_only: true

When enabled:

• All incoming group and DM messages reach the agent (for reading and querying)
• The agent does NOT send any response back on WhatsApp
• The agent still responds when explicitly @mentioned (respecting the existing require_mention logic)

Use cases

• Monitor group chats silently (teacher monitoring student groups, team channels)
• Have the agent aware of conversation context without engaging
• Privacy-conscious setups where the agent reads but doesn't auto-reply
• Receive message summaries on another platform (e.g., Telegram) without WhatsApp spam

Technical notes

The change would be in gateway/platforms/whatsapp.py:

• _build_message_event() already has _should_process_message() as a gate
• A new read_only check could be added at the adapter level to forward messages to the agent but suppress outgoing responses
• The bridge's Node.js bridge.js already distinguishes @mentions and reply-to-bot patterns

Current workaround

Setting require_mention: false + dm_policy: open allows the agent to see all messages but causes automatic responses to every message. Not ideal for silent monitoring.