Forum topics fixes: link opening, WebP sticker crash, reaction badge

- Fix forum message link opening: load forum topic when messageTopicId
  is set but forumTopic is null (shows correct topic header)
- Fix WebP sticker crash in ChatHeaderView: check sticker.format instead
  of sticker.fullType to determine ImageFile vs GifFile
- Fix reaction badge icon size: use 16f to match TGChat pattern

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: japananimetime

app/src/main/java/org/thunderdog/challegram/component/chat/ChatHeaderView.java

@@ -109,18 +109,26 @@ private void loadTopicEmojiFiles () {
     }
 
     int size = Screen.dp(40f); // Avatar size
-    if (sticker.fullType instanceof TdApi.StickerFullTypeRegular) {
-      topicImageFile = new ImageFile(tdlib, sticker.sticker);
-      topicImageFile.setSize(size);
-      topicImageFile.setScaleType(ImageFile.CENTER_CROP);
-      topicGifFile = null;
-      topicIconReceiver.getImageReceiver(0).requestFile(topicImageFile);
-    } else {
-      topicGifFile = new GifFile(tdlib, sticker);
-      topicGifFile.setOptimizationMode(GifFile.OptimizationMode.EMOJI);
-      topicGifFile.setRequestedSize(size);
-      topicImageFile = null;
-      topicIconReceiver.getGifReceiver(0).requestFile(topicGifFile);
+    // Check sticker format to determine file type
+    // WebP stickers use ImageFile, TGS and WEBM use GifFile
+    switch (sticker.format.getConstructor()) {
+      case TdApi.StickerFormatWebp.CONSTRUCTOR: {
+        topicImageFile = new ImageFile(tdlib, sticker.sticker);
+        topicImageFile.setSize(size);
+        topicImageFile.setScaleType(ImageFile.CENTER_CROP);
+        topicGifFile = null;
+        topicIconReceiver.getImageReceiver(0).requestFile(topicImageFile);
+        break;
+      }
+      case TdApi.StickerFormatTgs.CONSTRUCTOR:
+      case TdApi.StickerFormatWebm.CONSTRUCTOR: {
+        topicGifFile = new GifFile(tdlib, sticker);
+        topicGifFile.setOptimizationMode(GifFile.OptimizationMode.EMOJI);
+        topicGifFile.setRequestedSize(size);
+        topicImageFile = null;
+        topicIconReceiver.getGifReceiver(0).requestFile(topicGifFile);
+        break;
+      }
     }
   }
 

app/src/main/java/org/thunderdog/challegram/ui/ForumTopicView.java

@@ -280,10 +280,11 @@ public void setTopic (Tdlib tdlib, TdApi.ForumTopic topic, @Nullable String high
     }
 
     // Reactions counter - show if there are unread reactions
+    // Using same pattern as TGChat: baseline_favorite_14 icon at 16f size
     if (topic.unreadReactionCount > 0) {
       if (reactionsCounter == null) {
         reactionsCounter = new Counter.Builder()
-          .drawable(R.drawable.baseline_favorite_14, 14f, 0f, Gravity.CENTER)
+          .drawable(R.drawable.baseline_favorite_14, 16f, 0f, Gravity.CENTER)
           .callback(this)
           .build();
       }

app/src/main/java/org/thunderdog/challegram/ui/MessagesController.java

@@ -2818,6 +2818,26 @@ private void updateView () {
       updateForcedSubtitle(); // must be called before calling headerCell.setChat
       headerCell.setCallback(areScheduled ? null : this);
     }
+
+    // Load forum topic if we have a messageTopicId but no forumTopic
+    // This happens when opening a message via link in a forum
+    if (forumTopic == null && messageTopicId != null &&
+        messageTopicId.getConstructor() == TdApi.MessageTopicForum.CONSTRUCTOR) {
+      long forumTopicId = ((TdApi.MessageTopicForum) messageTopicId).messageThreadId;
+      tdlib.client().send(new TdApi.GetForumTopic(chat.id, (int) forumTopicId), result -> {
+        if (result.getConstructor() == TdApi.ForumTopic.CONSTRUCTOR) {
+          runOnUiThreadOptional(() -> {
+            forumTopic = (TdApi.ForumTopic) result;
+            // Update header with loaded topic
+            TdApi.Chat hChat = messageThread != null ? tdlib.chatSync(messageThread.getContextChatId()) : null;
+            headerCell.setChat(tdlib, hChat != null ? hChat : chat, messageThread, forumTopic);
+            // Update unread counts
+            updateCounters(true);
+          });
+        }
+      });
+    }
+
     TdApi.Chat headerChat = messageThread != null ? tdlib.chatSync(messageThread.getContextChatId()) : null;
     headerCell.setChat(tdlib, headerChat != null ? headerChat : chat, messageThread, forumTopic);