fix(discord): add media dedup production code for messaging tool pipeline

Wire media URL tracking through the embedded agent pipeline so that
media already sent via messaging tools is not delivered again by the
reply dispatcher.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/auto-reply/reply/reply-payloads.ts

@@ -95,6 +95,31 @@ export function filterMessagingToolDuplicates(params: {
   return payloads.filter((payload) => !isMessagingToolDuplicate(payload.text ?? "", sentTexts));
 }
 
+export function filterMessagingToolMediaDuplicates(params: {
+  payloads: ReplyPayload[];
+  sentMediaUrls: string[];
+}): ReplyPayload[] {
+  const { payloads, sentMediaUrls } = params;
+  if (sentMediaUrls.length === 0) {
+    return payloads;
+  }
+  const sentSet = new Set(sentMediaUrls);
+  return payloads.map((payload) => {
+    const mediaUrl = payload.mediaUrl;
+    const mediaUrls = payload.mediaUrls;
+    const stripSingle = mediaUrl && sentSet.has(mediaUrl);
+    const filteredUrls = mediaUrls?.filter((u) => !sentSet.has(u));
+    if (!stripSingle && (!mediaUrls || filteredUrls?.length === mediaUrls.length)) {
+      return payload; // No change
+    }
+    return {
+      ...payload,
+      mediaUrl: stripSingle ? undefined : mediaUrl,
+      mediaUrls: filteredUrls?.length ? filteredUrls : undefined,
+    };
+  });
+}
+
 function normalizeAccountId(value?: string): string | undefined {
   const trimmed = value?.trim();
   return trimmed ? trimmed.toLowerCase() : undefined;