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/app/update/instances.rs

@@ -0,0 +1,161 @@
+//! 实例页「启动参数」区的消息落点（M157）。
+//!
+//! 三件事：
+//! 1. **编辑**只改页面状态（`App::launch_form`）并置脏——不 dispatch，不打网络；
+//! 2. **保存**派一条 [`AppCommand::SetInstanceLaunchArgs`]（整份五项补丁），回程由
+//!    `InstancesChanged` 快照刷新页面（不做乐观回显，与 M90 的启动/停止同一条纪律）；
+//! 3. **恢复跟随全局**只清表单（仍需用户点保存）——「点一下就写盘」会让误触直接生效。
+//!
+//! 脏标记的清理点在保存之后：`refresh_view` 的 `LaunchForm::sync` 看到「同实例 + 脏」不会覆盖，
+//! 所以保存后要显式清脏，让下一次快照（host 写完文件回来的那份）重播种。
+
+use iced::Task;
+use unlucky_presenter::dto::{AppCommand, LaunchArgsPatch};
+
+use crate::pages::InstanceMessage;
+
+use super::super::message::Message;
+use super::super::state::App;
+
+impl App {
+    /// 启动参数区的一条消息。
+    pub(super) fn on_instance_message(&mut self, message: InstanceMessage) -> Task<Message> {
+        let Some(instance) = self.selected_instance_id() else {
+            return Task::none();
+        };
+        if !self.launch_form.bound_to(&instance) {
+            // 表单还没对着这个实例（首帧还没播种）：不接编辑，免得改到别的实例上。
+            return Task::none();
+        }
+
+        match message {
+            InstanceMessage::Jvm(text) => {
+                self.launch_form.jvm = text;
+                self.launch_form.dirty = true;
+            }
+            InstanceMessage::Game(text) => {
+                self.launch_form.game = text;
+                self.launch_form.dirty = true;
+            }
+            InstanceMessage::Memory(text) => {
+                self.launch_form.memory = text;
+                self.launch_form.dirty = true;
+            }
+            InstanceMessage::Java(text) => {
+                self.launch_form.java = text;
+                self.launch_form.dirty = true;
+            }
+            InstanceMessage::Backend(id) => {
+                self.launch_form.backend = id;
+                self.launch_form.dirty = true;
+            }
+            InstanceMessage::Reset => {
+                self.launch_form.reset();
+            }
+            InstanceMessage::Save => {
+                let patch: LaunchArgsPatch = self.launch_form.patch();
+                self.launch_form.dirty = false;
+                self.dispatch(AppCommand::set_launch_args(&instance, patch));
+            }
+        }
+        // 纯本地编辑：不重建视图模型（页面直接从表单画），只要一帧重绘即可——iced 在
+        // 消息处理完之后本来就会画一帧，所以这里什么都不排。
+        Task::none()
+    }
+
+    /// 详情页当前选中的实例 id（不在详情页时为 `None`）。
+    fn selected_instance_id(&self) -> Option<String> {
+        match self.state.route() {
+            unlucky_presenter::router::Route::Detail(id) => Some(id.clone()),
+            _ => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use unlucky_design::color::SchemeFlavor;
+    use unlucky_presenter::dto::LaunchArgsView;
+    use unlucky_presenter::settings_bridge::SettingsBridge;
+
+    use crate::app::state::App;
+    use crate::cli::Options;
+    use crate::pages::{InstanceMessage, LaunchForm};
+
+    use crate::theme::Families;
+
+    const FAMILIES: Families = Families {
+        text: "Segoe UI",
+        display: "Segoe UI",
+        mono: "Consolas",
+    };
+
+    fn app_with_form() -> App {
+        let mut app = App::with_presenter(
+            Options::default(),
+            FAMILIES,
+            SchemeFlavor::Light,
+            Box::new(unlucky_presenter::mock::MockBackend::new()),
+            SettingsBridge::memory_only(),
+        );
+        // 进详情页 + 直接放一份「已播种」的表单：本测试只验消息落点，
+        // 不验播种（那在 `LaunchForm::sync` 的单测里）。
+        app.state.navigate(unlucky_presenter::router::Route::Detail(
+            INSTANCE.to_string(),
+        ));
+        app.launch_form = LaunchForm::from_view(
+            Some(INSTANCE),
+            &LaunchArgsView {
+                instance_id: INSTANCE.to_string(),
+                ..LaunchArgsView::default()
+            },
+        );
+        app
+    }
+
+    /// 测试用的实例 id（mock 后端的实例快照里有它）。
+    const INSTANCE: &str = "survival";
+
+    /// 编辑 → 脏；恢复 → 五项清空仍需保存；保存前不发命令。
+    #[test]
+    fn editing_marks_dirty_and_reset_waits_for_save() {
+        let mut app = app_with_form();
+        let _ = app.on_instance_message(InstanceMessage::Memory("6144".to_string()));
+        assert_eq!(app.launch_form.memory, "6144");
+        assert!(app.launch_form.dirty);
+
+        let _ = app.on_instance_message(InstanceMessage::Backend("vulkan".to_string()));
+        assert_eq!(app.launch_form.backend, "vulkan");
+
+        let _ = app.on_instance_message(InstanceMessage::Reset);
+        assert_eq!(app.launch_form.memory, "");
+        assert_eq!(app.launch_form.backend, "default");
+        assert!(app.launch_form.dirty, "恢复之后还得点保存才落盘");
+    }
+
+    /// 表单没绑定到当前实例时不接编辑（否则草稿会写到别的实例上）。
+    #[test]
+    fn edits_are_ignored_when_the_form_is_bound_elsewhere() {
+        let mut app = app_with_form();
+        app.launch_form = LaunchForm::from_view(
+            Some("other"),
+            &LaunchArgsView {
+                instance_id: "other".to_string(),
+                ..LaunchArgsView::default()
+            },
+        );
+        let _ = app.on_instance_message(InstanceMessage::Memory("9999".to_string()));
+        assert_eq!(app.launch_form.memory, "");
+        assert!(!app.launch_form.dirty);
+    }
+
+    /// 保存之后脏标记清掉（否则下一次快照刷新不敢重播种，界面会一直显示旧值）。
+    #[test]
+    fn save_clears_the_dirty_flag() {
+        let mut app = app_with_form();
+        let _ = app.on_instance_message(InstanceMessage::Java("D:/jdk21/bin/java.exe".to_string()));
+        assert!(app.launch_form.dirty);
+        let _ = app.on_instance_message(InstanceMessage::Save);
+        assert!(!app.launch_form.dirty);
+    }
+}