fix(worker): reactorJid null guard, document reaction removal, restore comments

apps/worker/src/whatsapp/normalizer.ts

@@ -22,7 +22,9 @@ export function normalizeMessage(
   if (!key) return null;
 
   const remoteJid = key.remoteJid ?? '';
+  // only group messages (group JIDs end with @g.us)
   if (!remoteJid.endsWith('@g.us')) return null;
+  // skip our own outgoing messages
   if (key.fromMe) return null;
   if (!msg.message) return null;
 
@@ -49,7 +51,9 @@ export function normalizeReaction(
   if (!key) return null;
 
   const remoteJid = key.remoteJid ?? '';
+  // only group messages (group JIDs end with @g.us)
   if (!remoteJid.endsWith('@g.us')) return null;
+  // skip our own outgoing messages
   if (key.fromMe) return null;
 
   const reaction = msg.message?.reactionMessage;
@@ -58,10 +62,15 @@ export function normalizeReaction(
   const targetMsgId = reaction.key?.id;
   if (!targetMsgId) return null;
 
+  // Ensure reactorJid is not empty (group message must have a participant)
+  const reactorJid = key.participant;
+  if (!reactorJid) return null;
+
   return {
-    reactorJid: key.participant ?? '',
+    reactorJid,
     targetMsgId,
     sourceGroupJid: remoteJid,
+    // emoji is empty string ('') when reaction was removed (retraction)
     emoji: reaction.text ?? '',
     accountId,
   };