fix(telegram): ignore message_thread_id for non-forum group sessions

Regular Telegram groups (without Topics/Forums enabled) can send
message_thread_id when users reply to messages. This was incorrectly
being used to create separate session keys like '-123:topic:42',
causing each reply chain to get its own conversation context.

Now resolveTelegramForumThreadId only returns a thread ID when the
chat is actually a forum (is_forum=true). For regular groups, the
thread ID is ignored, ensuring all messages share the same session.

DMs continue to use messageThreadId for thread sessions as before.

src/telegram/bot-native-commands.ts

@@ -421,7 +421,8 @@ export const registerTelegramNativeCommands = ({
             },
           });
           const baseSessionKey = route.sessionKey;
-          const dmThreadId = !isGroup ? resolvedThreadId : undefined;
+          // DMs: use raw messageThreadId for thread sessions (not resolvedThreadId which is for forums)
+          const dmThreadId = !isGroup ? messageThreadId : undefined;
           const threadKeys =
             dmThreadId != null
               ? resolveThreadSessionKeys({ baseSessionKey, threadId: String(dmThreadId) })