feat(launch): M157 实例级启动参数（五项回落 + graphicsBackend 三态）

core: 新增 game/launch_overrides（LaunchOverrides 五项 All-Option + 三级回落 + 文本补丁校验）与 launch/overrides（拼装落位：全局 java.extra_args 进 user.jvm、实例 jvmArgs 进 override_jvm、gameArgs 进 user.game、memory 进 -Xmx、backend 进 --graphicsBackend 并复用既有版本门槛告警）；实例 schema 登记 launch.* 五键。

presenter: dto/LaunchArgsView+LaunchArgsPatch，主机侧读/写与门槛判定（backend_allowed），AppCommand::SetInstanceLaunchArgs。

cli: 新命令 instances launch-args（读/写/--clear），launch 装配链消费回落值。

app-iced: 实例详情页「启动参数」区（JVM/游戏参数、内存、Java、三态后端 chips + 灰化提示 + 保存/恢复），表单状态归 App、i18n 中英文案同步。

crates/app-iced/src/pages/tests.rs

@@ -54,10 +54,11 @@ fn screens_declare_the_layout_their_page_needs() {
 #[test]
 fn every_screen_builds_at_the_three_comparison_widths() {
     let ui = ui();
+    let form = demo_launch_form();
     for width in [1180.0, 900.0, 700.0] {
         for screen in Screen::ALL {
             let model = demo_model(screen, width);
-            let _element: Element<'_, Message> = app(&ui, &model);
+            let _element: Element<'_, Message> = app(&ui, &model, &form);
         }
     }
 }
@@ -66,9 +67,10 @@ fn every_screen_builds_at_the_three_comparison_widths() {
 #[test]
 fn an_empty_snapshot_still_builds() {
     let ui = ui();
+    let form = demo_launch_form();
     for screen in Screen::ALL {
         let model = Model::new(screen, 1180.0, Some(screen.nav()));
-        let _element: Element<'_, Message> = app(&ui, &model);
+        let _element: Element<'_, Message> = app(&ui, &model, &form);
     }
 }