fix(platform): skip duplicate announcement hub mirrors on re-gossip

Before inserting a remote hub mirror, check announcementHub.isDuplicateMirror
for the source messageId and record markMirrored after a successful insert.
Prevents duplicate 📡 mirror lines when ANNOUNCEMENT_HUB_POST is received twice.

Co-authored-by: Cursor <[email protected]>

index.js

@@ -2535,6 +2535,7 @@ class PearcordPlatform extends EventEmitter {
     )
     const out = []
     const savedGuildId = this.guild?.guild?.id
+    const hubMessageId = payload.messageId || null
     for (const sub of subs) {
       try {
         const channels = await this.db.find(COLLECTIONS.CHANNELS, {
@@ -2542,6 +2543,16 @@ class PearcordPlatform extends EventEmitter {
         })
         const tch = channels.find((c) => c.id === sub.targetChannelId)
         if (!tch || tch.type !== 'text') continue
+        if (hubMessageId) {
+          const dup = await this.announcementHub.isDuplicateMirror({
+            subscriberGuildId: sub.subscriberGuildId,
+            targetChannelId: sub.targetChannelId,
+            sourceGuildId: payload.sourceGuildId,
+            sourceChannelId: payload.sourceChannelId,
+            messageId: hubMessageId
+          })
+          if (dup) continue
+        }
         if (savedGuildId !== sub.subscriberGuildId) {
           await this.loadGuild(sub.subscriberGuildId)
         }
@@ -2551,6 +2562,17 @@ class PearcordPlatform extends EventEmitter {
           content: body,
           authorId: payload.authorId || this.identity?.user?.id
         })
+        if (hubMessageId) {
+          await this.announcementHub.markMirrored({
+            subscriberGuildId: sub.subscriberGuildId,
+            targetChannelId: sub.targetChannelId,
+            sourceGuildId: payload.sourceGuildId,
+            sourceChannelId: payload.sourceChannelId,
+            messageId: hubMessageId,
+            localMessageId: row.id,
+            postedAt: payload.postedAt
+          })
+        }
         out.push(row)
       } catch {
         // skip invalid sub