fix: 修复实例分组无法保存的问题

direct-link（外部 .minecraft 关联）同步逻辑会把来源路径当作分组名
写入 instance_groups 表，每次同步都覆盖用户手动设置的分组，导致
分组当场生效、重启丢失。

移除三处 direct-link 相关的来源分组写入，使 instance_groups 表
专属于用户分组：
- sync_direct_link_instances: 同步时不再覆盖 groups
- create_direct_link_instance: 建实例时不再写来源分组
- launcher::promote_external_instance_link: 提升外部实例时不再写分组

packages/app-lib/src/launcher/mod.rs

@@ -1,5 +1,4 @@
 //! Logic for launching Minecraft
-use crate::api::pack::import::direct_link::direct_link_group;
 use crate::data::ModLoader;
 use crate::event::emit::{emit_instance, emit_loading, init_loading};
 use crate::event::{InstancePayloadType, LoadingBarType};
@@ -717,14 +716,6 @@ async fn promote_external_instance_link(
         &mut tx,
     )
     .await?;
-    if let Some(group) = direct_link_group(&direct.dot_minecraft) {
-        crate::state::instances::adapters::sqlite::instance_rows::replace_instance_groups(
-            &instance.id,
-            &[group],
-            &mut tx,
-        )
-        .await?;
-    }
     tx.commit().await?;
     emit_instance(&instance.id, InstancePayloadType::Edited).await?;
     Ok(())