重构会话页面的消息渲染，支持块级虚拟化，提升长会话性能，减少卡断

src-tauri/src/parsers/opencode.rs

@@ -667,9 +667,10 @@ fn group_into_turns(messages: Vec<UnifiedMessage>) -> Vec<MessageTurn> {
             let timestamp = msg.timestamp;
             i += 1;
 
+            // Only absorb immediately following Tool messages
+            // (stop at the next assistant message to keep turns small for virtualization)
             while i < messages.len()
-                && (matches!(messages[i].role, MessageRole::Assistant)
-                    || matches!(messages[i].role, MessageRole::Tool))
+                && matches!(messages[i].role, MessageRole::Tool)
             {
                 blocks.extend(messages[i].content.clone());
                 if usage.is_none() {