tweak: ensure synthetic user message following subtasks is only added when user manually invoked subtask

packages/opencode/src/session/prompt.ts

@@ -454,6 +454,7 @@ export namespace SessionPrompt {
           } satisfies MessageV2.ToolPart)
         }
 
+        if (task.command) {
           // Add synthetic user message to prevent certain reasoning models from erroring
           // If we create assistant messages w/ out user ones following mid loop thinking signatures
           // will be missing and it can cause errors for models like gemini for example
@@ -476,6 +477,7 @@ export namespace SessionPrompt {
             text: "Summarize the task tool output above and continue with your task.",
             synthetic: true,
           } satisfies MessageV2.TextPart)
+        }
 
         continue
       }