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/presenter/src/host/launch.rs

@@ -52,9 +52,28 @@ pub struct JavaPick {
     pub summary: String,
 }
 
-/// 选一个能用的 Java：托管 > JAVA_HOME > PATH（`core::game::java` 的探测与优先级）。
-pub fn pick_java(env: &HostEnv, version_id: &str) -> JavaPick {
+/// 选一个能用的 Java：显式路径（实例 → 全局 `java.selected_path`）> 托管 > JAVA_HOME > PATH。
+///
+/// 显式路径**先探测**（`java -version`）：探测失败不报错，按版本要求的基准主版本兜底——
+/// 与自动挑的退路同一口径（启动路径不该因为探测不到就拒绝启动）。
+pub fn pick_java(env: &HostEnv, version_id: &str, explicit: Option<&std::path::Path>) -> JavaPick {
     let store = env.store();
+    let required = unlucky_core::game::java::requirement_for_version(&env.game, version_id);
+    if let Some(path) = explicit {
+        let runtime = unlucky_core::game::java::probe::probe(
+            path,
+            unlucky_core::game::java::probe::JavaOrigin::Instance,
+        );
+        let major = runtime.major.unwrap_or(required.minimum);
+        return JavaPick {
+            selection: JavaSelection::new(runtime.binary.clone(), major, runtime.bits),
+            summary: format!(
+                "实例指定 Java {}（{}）",
+                runtime.version.clone().unwrap_or_else(|| major.to_string()),
+                path.display()
+            ),
+        };
+    }
     let install_root = store
         .doc()
         .effective_str("java.installRoot")
@@ -69,7 +88,6 @@ pub fn pick_java(env: &HostEnv, version_id: &str) -> JavaPick {
         &ProcessEnv,
     );
     let candidates = unlucky_core::game::java::candidates_in_roots(&roots);
-    let required = unlucky_core::game::java::requirement_for_version(&env.game, version_id);
     let picked = unlucky_core::game::java::pick(&candidates, &required).cloned();
     match picked {
         Some(runtime) => {
@@ -201,18 +219,14 @@ pub fn build_request(
         game_assets: assets_root,
     };
 
-    let java = pick_java(env, &version_id);
+    let overrides = super::launch_args::resolved(env, &target.id);
+    let java = pick_java(env, &version_id, overrides.java_path.as_deref());
     let (auth, identity_line) = super::identity::resolve(env, target.account.as_deref())?;
-    let memory = env
-        .store()
-        .effective("java.default_memory_mb")
-        .and_then(serde_json::Value::as_u64)
-        .and_then(|value| u32::try_from(value).ok());
     let options = AdapterOptions {
         java: java.selection,
         memory: MemoryOptions {
             min_mb: None,
-            max_mb: memory,
+            max_mb: Some(overrides.memory_mb),
         },
         auth,
         launcher_name: LAUNCHER_NAME.to_string(),
@@ -227,6 +241,8 @@ pub fn build_request(
     let mut request = output.request;
     request.instance.id = target.id.clone();
     request.instance.name = target.name.clone();
+    // 实例级启动参数（三级回落后的生效值）最后落位：user.* / memory / graphics_backend。
+    unlucky_core::launch::overrides::apply(&mut request, &overrides);
     Ok((request, warnings))
 }