Fix mention profile fetch for mention_index blocks

Closes: https://github.com/damus-io/damus/issues/3344
Changelog-Fixed: Ensure mention profile prefetch covers mention_index blocks
Signed-off-by: alltheseas <64376233+alltheseas@users.noreply.github.com>

damus/Features/Events/NoteContentView.swift

@@ -281,15 +281,10 @@ struct NoteContentView: View {
 
         var mentionPubkeys: Set<Pubkey> = []
         let _: ()? = try? blockGroup.forEachBlock({ _, block in
-            switch block {
-            case .mention(let mentionBlock):
-                if let mention = MentionRef(block: mentionBlock),
-                   let pubkey = mention.pubkey {
+            guard let pubkey = block.mentionPubkey(tags: event.tags) else {
+                return .loopContinue
+            }
             mentionPubkeys.insert(pubkey)
-                }
-            default:
-                break
-            }
             return .loopContinue
         })
 
@@ -609,3 +604,26 @@ func separate_images(ndb: Ndb, ev: NostrEvent, keypair: Keypair) -> [MediaUrl]?
     let mediaUrls = urlBlocks.map { MediaUrl.image($0) }
     return mediaUrls.isEmpty ? nil : mediaUrls
 }
+
+extension NdbBlock {
+    func mentionPubkey(tags: Tags) -> Pubkey? {
+        switch self {
+        case .mention(let mentionBlock):
+            guard let mention = MentionRef(block: mentionBlock) else {
+                return nil
+            }
+            return mention.pubkey
+        case .mention_index(let mentionIndex):
+            let tagPosition = Int(mentionIndex)
+            guard tagPosition >= 0, tagPosition < tags.count else {
+                return nil
+            }
+            guard let mention = MentionRef.from_tag(tag: tags[tagPosition]) else {
+                return nil
+            }
+            return mention.pubkey
+        default:
+            return nil
+        }
+    }
+}