fix(whatsapp): update reaction docs + suppress pairing for reactions

- Update docs: reaction removals now emit events with isRemoval=true
- Pass no-op sendMessage to access control to prevent pairing messages
  being sent when unknown users react (pairing is for messages, not reactions)

(Cursor review)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/channels/whatsapp.md

@@ -304,9 +304,10 @@ When someone reacts to a message in a WhatsApp chat, the gateway emits a system
 
 ```
 WhatsApp reaction added: 👍 by +1234567890 msg BAE5ABC123
+WhatsApp reaction removed by +1234567890 msg BAE5ABC123
 ```
 
-- Reaction removals (empty emoji) are silently skipped.
+- Reaction removals emit events with `isRemoval: true` and no emoji in the message.
 - Self-reactions in DMs are correctly attributed to the bot's own JID.
 - Group reactions include the participant who reacted.
 - Events are deduplicated by message ID, sender, and emoji to avoid repeat notifications.

src/web/inbound/monitor.ts

@@ -357,6 +357,7 @@ export async function monitorWebInbox(options: {
           if (!isOwnReaction) {
             const from = group ? chatJid : await resolveInboundJid(chatJid);
             if (!from) continue;
+            // No-op sendMessage: reactions shouldn't trigger pairing replies
             const access = await checkInboundAccessControl({
               accountId: options.accountId,
               from,
@@ -365,7 +366,7 @@ export async function monitorWebInbox(options: {
               group,
               isFromMe: false,
               connectedAtMs,
-              sock: { sendMessage: (jid, content) => sock.sendMessage(jid, content) },
+              sock: { sendMessage: async () => ({}) },
               remoteJid: chatJid,
             });
             if (!access.allowed) {