feat: 一键安装支持自选游戏目录

StarLight 实例一键安装此前固定落到启动器默认目录，无法选择游戏数据位置。
现复用创建流程的外部游戏目录能力：点击一键安装后弹出目录选择框，
只允许修改游戏目录，其余参数仍由服务器整合包决定。

- hosted::create 接受 game_dir_root，拼为 <root>/<包名> 作为 game_dir_override
  （刻意避开 versions/ 布局，该结构被外部直链实例检测占用）
- 新增顶层命令 get_launcher_root_dir，作为弹窗默认值（可执行文件所在目录）
- 新增 HostedGameDirModal 弹窗：只读路径框 + 浏览 + 默认位置 + 安装预览
- 补齐 en-US / zh-CN / zh-TW 三语文案

hosted_create 增加 game_dir_root 参数，前端 hostedCreate/install 同步透传。

apps/app-frontend/src/components/instance/HostedGameDirModal.vue

@@ -0,0 +1,161 @@
+<template>
+	<NewModal
+		ref="modal"
+		:header="formatMessage(messages.header)"
+		max-width="560px"
+		:on-hide="handleHide"
+	>
+		<div class="flex flex-col gap-4">
+			<p class="m-0 text-secondary">
+				{{ formatMessage(messages.description) }}
+			</p>
+
+			<div class="flex flex-col gap-2">
+				<span class="font-semibold text-contrast">
+					{{ formatMessage(messages.gameDirLabel) }}
+				</span>
+				<div class="flex gap-2">
+					<StyledInput
+						class="flex-1"
+						:model-value="selectedPath"
+						readonly
+						:placeholder="defaultPath || formatMessage(messages.noSelection)"
+					/>
+					<ButtonStyled>
+						<button type="button" @click="browse">
+							<FolderOpenIcon />
+							{{ formatMessage(messages.browse) }}
+						</button>
+					</ButtonStyled>
+				</div>
+				<button
+					v-if="defaultPath && selectedPath !== defaultPath"
+					type="button"
+					class="self-start text-sm text-brand underline decoration-transparent underline-offset-2 transition-colors hover:decoration-current"
+					@click="selectedPath = defaultPath"
+				>
+					{{ formatMessage(messages.resetDefault) }}
+				</button>
+			</div>
+
+			<p v-if="previewPath" class="m-0 text-sm text-secondary break-all">
+				{{ formatMessage(messages.preview, { path: previewPath }) }}
+			</p>
+		</div>
+
+		<template #actions>
+			<div class="flex justify-end gap-2">
+				<ButtonStyled type="outlined">
+					<button type="button" @click="handleCancel">
+						<XIcon />
+						{{ formatMessage(commonMessages.cancelButton) }}
+					</button>
+				</ButtonStyled>
+				<ButtonStyled color="brand">
+					<button type="button" :disabled="!selectedPath" @click="handleConfirm">
+						<CheckIcon />
+						{{ formatMessage(messages.confirm) }}
+					</button>
+				</ButtonStyled>
+			</div>
+		</template>
+	</NewModal>
+</template>
+
+<script setup lang="ts">
+import { CheckIcon, FolderOpenIcon, XIcon } from '@modrinth/assets'
+import {
+	ButtonStyled,
+	commonMessages,
+	defineMessages,
+	injectFilePicker,
+	NewModal,
+	StyledInput,
+	useVIntl,
+} from '@modrinth/ui'
+import { invoke } from '@tauri-apps/api/core'
+import { computed, ref } from 'vue'
+
+const emit = defineEmits<{
+	(e: 'confirm', gameDirRoot: string): void
+	(e: 'cancel'): void
+}>()
+
+const { formatMessage } = useVIntl()
+const filePicker = injectFilePicker()
+const modal = ref<InstanceType<typeof NewModal>>()
+const defaultPath = ref('')
+const selectedPath = ref('')
+const accepted = ref(false)
+
+const messages = defineMessages({
+	header: {
+		id: 'app.hosted-install.game-dir.header',
+		defaultMessage: 'Choose game directory',
+	},
+	description: {
+		id: 'app.hosted-install.game-dir.description',
+		defaultMessage:
+			'StarLight instance data (mods, saves, configs, resource packs) is stored in an external game directory. Pick a root folder — the modpack gets its own subfolder inside it.',
+	},
+	gameDirLabel: {
+		id: 'app.hosted-install.game-dir.label',
+		defaultMessage: 'Game directory root',
+	},
+	browse: {
+		id: 'app.hosted-install.game-dir.browse',
+		defaultMessage: 'Browse',
+	},
+	noSelection: {
+		id: 'app.hosted-install.game-dir.no-selection',
+		defaultMessage: 'No folder selected',
+	},
+	resetDefault: {
+		id: 'app.hosted-install.game-dir.reset-default',
+		defaultMessage: 'Use default location',
+	},
+	preview: {
+		id: 'app.hosted-install.game-dir.preview',
+		defaultMessage: 'Game files will be installed to: {path}',
+	},
+	confirm: {
+		id: 'app.hosted-install.game-dir.confirm',
+		defaultMessage: 'Install',
+	},
+})
+
+const previewPath = computed(() => {
+	const base = (selectedPath.value ?? '').replace(/[\\/]+$/, '')
+	return base ? `${base}/<pack name>` : ''
+})
+
+async function show() {
+	if (!defaultPath.value) {
+		defaultPath.value = await invoke<string>('get_launcher_root_dir').catch(() => '')
+	}
+	if (!selectedPath.value) selectedPath.value = defaultPath.value
+	accepted.value = false
+	modal.value?.show()
+}
+
+async function browse() {
+	const picked = await filePicker.pickFolder?.()
+	if (picked?.path) selectedPath.value = picked.path
+}
+
+function handleCancel() {
+	modal.value?.hide()
+}
+
+function handleConfirm() {
+	accepted.value = true
+	modal.value?.hide()
+	emit('confirm', selectedPath.value)
+}
+
+function handleHide() {
+	if (!accepted.value) emit('cancel')
+}
+
+defineExpose({ show })
+</script>

apps/app-frontend/src/composables/useHostedCreation.ts

@@ -23,7 +23,7 @@ export function useHostedCreation() {
 			completed.value = false
 		}
 	}
-	async function install() {
+	async function install(gameDirRoot?: string | null) {
 		if (installing.value) return
 		installing.value = true
 		installError.value = ''
@@ -40,7 +40,7 @@ export function useHostedCreation() {
 				}
 			}
 			if (completed.value) return createdInstance.value
-			createdInstance.value ??= await hostedCreate()
+			createdInstance.value ??= await hostedCreate(gameDirRoot)
 			const instanceId = createdInstance.value
 			await hostedSync(instanceId)
 			if (attempt !== generation) return

apps/app-frontend/src/helpers/hosted-packs.ts

@@ -99,7 +99,10 @@ export interface HostedSyncResult {
 }
 export const hostedDefault = () =>
 	invokeWithSession<HostedPublication>('plugin:install|hosted_default')
-export const hostedCreate = () => invokeWithSession<string>('plugin:install|hosted_create')
+export const hostedCreate = (gameDirRoot?: string | null) =>
+	invokeWithSession<string>('plugin:install|hosted_create', {
+		gameDirRoot: gameDirRoot ?? null,
+	})
 export const hostedBinding = (instanceId: string) =>
 	invokeHosted<HostedBinding | null>('plugin:install|hosted_binding', { instanceId })
 export const hostedSync = (instanceId: string) => {

apps/app-frontend/src/locales/en-US/index.json

@@ -29,6 +29,14 @@
   "app.hosted-packs.auto-installing": { "message": "Downloading and installing the server modpack…" },
   "app.hosted-packs.auto-description": { "message": "Download and automatically install the modpack from StarLight to play on the StarLight server with one click." },
   "app.hosted-packs.auto-install": { "message": "Install the StarLight modpack" },
+  "app.hosted-install.game-dir.header": { "message": "Choose game directory" },
+  "app.hosted-install.game-dir.description": { "message": "StarLight instance data (mods, saves, configs, resource packs) is stored in an external game directory. Pick a root folder — the modpack gets its own subfolder inside it." },
+  "app.hosted-install.game-dir.label": { "message": "Game directory root" },
+  "app.hosted-install.game-dir.browse": { "message": "Browse" },
+  "app.hosted-install.game-dir.no-selection": { "message": "No folder selected" },
+  "app.hosted-install.game-dir.reset-default": { "message": "Use default location" },
+  "app.hosted-install.game-dir.preview": { "message": "Game files will be installed to: {path}" },
+  "app.hosted-install.game-dir.confirm": { "message": "Install" },
   "app.onboarding.instance-mode.title": { "message": "Choose your instance type" },
   "app.onboarding.instance-mode.description": { "message": "StarLight automatically installs the administrator-selected modpack and versions, then checks and completes updates before every launch. A StarLight login is required. Choose Local to select your own versions and modpacks for other servers or single-player." },
   "app.instance-mode.title": { "message": "Instance type" },

apps/app-frontend/src/locales/zh-CN/index.json

@@ -29,6 +29,14 @@
   "app.hosted-packs.auto-installing": { "message": "正在下载并安装服务器整合包…" },
   "app.hosted-packs.auto-description": { "message": "从StarLight服务器获取整合包并自动安装，可一键游玩StarLight服务器" },
   "app.hosted-packs.auto-install": { "message": "安装 StarLight 官方整合包" },
+  "app.hosted-install.game-dir.header": { "message": "选择游戏目录" },
+  "app.hosted-install.game-dir.description": { "message": "StarLight 实例的游戏数据（mods、存档、配置、资源包）会存放在外部游戏目录中。请选择一个根目录，整合包会在其中单独建一个子文件夹。" },
+  "app.hosted-install.game-dir.label": { "message": "游戏目录根路径" },
+  "app.hosted-install.game-dir.browse": { "message": "浏览" },
+  "app.hosted-install.game-dir.no-selection": { "message": "尚未选择文件夹" },
+  "app.hosted-install.game-dir.reset-default": { "message": "使用默认位置" },
+  "app.hosted-install.game-dir.preview": { "message": "游戏文件将安装到：{path}" },
+  "app.hosted-install.game-dir.confirm": { "message": "安装" },
   "app.onboarding.instance-mode.title": { "message": "选择实例类型" },
   "app.onboarding.instance-mode.description": { "message": "StarLight 实例自动安装管理员指定的整合包和版本，每次启动先检查并完成更新，需要登录 StarLight 账号。本地实例可自选版本和整合包，适合第三方服务器与单人游玩。" },
   "app.instance-mode.title": { "message": "实例类型" },

apps/app-frontend/src/locales/zh-TW/index.json

@@ -12,6 +12,14 @@
   "app.hosted-packs.auto-installing": { "message": "正在下載並安裝伺服器整合包…" },
   "app.hosted-packs.auto-description": { "message": "從StarLight伺服器取得整合包並自動安裝，可一鍵遊玩StarLight伺服器" },
   "app.hosted-packs.auto-install": { "message": "安裝 StarLight 官方整合包" },
+  "app.hosted-install.game-dir.header": { "message": "選擇遊戲目錄" },
+  "app.hosted-install.game-dir.description": { "message": "StarLight 實例的遊戲資料（mods、存檔、設定、資源包）會存放在外部遊戲目錄中。請選擇一個根目錄，整合包會在其中另外建立一個子資料夾。" },
+  "app.hosted-install.game-dir.label": { "message": "遊戲目錄根路徑" },
+  "app.hosted-install.game-dir.browse": { "message": "瀏覽" },
+  "app.hosted-install.game-dir.no-selection": { "message": "尚未選擇資料夾" },
+  "app.hosted-install.game-dir.reset-default": { "message": "使用預設位置" },
+  "app.hosted-install.game-dir.preview": { "message": "遊戲檔案將安裝到：{path}" },
+  "app.hosted-install.game-dir.confirm": { "message": "安裝" },
   "app.onboarding.instance-mode.title": { "message": "選擇實例類型" },
   "app.onboarding.instance-mode.description": { "message": "StarLight 實例自動安裝管理員指定的整合包和版本，每次啟動先檢查並完成更新，需要登入 StarLight 帳號。本地實例可自行選擇版本和整合包，適合第三方伺服器與單人遊玩。" },
   "app.instance-mode.title": { "message": "實例類型" },

apps/app-frontend/src/pages/Create.vue

@@ -4,6 +4,7 @@ import { BigOptionButton, Button, defineMessages, useVIntl } from '@modrinth/ui'
 import { inject, ref, watch } from 'vue'
 import { useRouter } from 'vue-router'
 import InstanceModeOptions from '@/components/instance/InstanceModeOptions.vue'
+import HostedGameDirModal from '@/components/instance/HostedGameDirModal.vue'
 import HostedPackProgress from '@/components/instance/HostedPackProgress.vue'
 import type { InstanceMode } from '@/helpers/hosted-packs'
 import { useHostedCreation } from '@/composables/useHostedCreation'
@@ -15,6 +16,18 @@ const { installing, installError, createdInstance, completed, acknowledge, insta
 const instanceMode = ref<InstanceMode>(
 	installing.value || createdInstance.value ? 'starlight' : 'local',
 )
+
+const hostedGameDirModal = ref<InstanceType<typeof HostedGameDirModal>>()
+
+// One-click StarLight installs reuse the same external game-directory choice
+// as the custom creation flow: the pack gets its own folder under `<root>`.
+function promptHostedGameDir() {
+	hostedGameDirModal.value?.show()
+}
+
+async function installHostedWithGameDir(gameDirRoot: string) {
+	await install(gameDirRoot)
+}
 async function openCompleted(instanceId: string) {
 	try {
 		const failure = await router.push(`/instance/${encodeURIComponent(instanceId)}/`)
@@ -103,7 +116,12 @@ async function handleStartFresh() {
 			await openCompleted(createdInstance.value)
 			return
 		}
-		await install()
+		if (createdInstance.value) {
+			// A previous attempt already created the instance; retry in place.
+			await install()
+			return
+		}
+		promptHostedGameDir()
 		return
 	}
 	showModal?.({
@@ -179,6 +197,10 @@ function handleImportExisting() {
 				/>
 			</div>
 
+			<HostedGameDirModal
+				ref="hostedGameDirModal"
+				@confirm="installHostedWithGameDir"
+			/>
 			<HostedPackProgress :instance-id="createdInstance" :active="installing" />
 			<p v-if="installError" class="m-0 text-red" role="alert">{{ installError }}</p>
 			<p v-if="instanceMode === 'local'" class="m-0 text-sm text-secondary">

apps/app/src/api/install.rs

@@ -66,8 +66,10 @@ pub async fn hosted_default() -> Result<theseus::pack::hosted::Publication> {
 }
 
 #[tauri::command]
-pub async fn hosted_create() -> Result<String> {
-    Ok(theseus::pack::hosted::create().await?)
+pub async fn hosted_create(
+    game_dir_root: Option<String>,
+) -> Result<String> {
+    Ok(theseus::pack::hosted::create(game_dir_root).await?)
 }
 
 #[tauri::command]

apps/app/src/main.rs

@@ -232,6 +232,21 @@ async fn initialize_state(app: tauri::AppHandle) -> api::Result<()> {
     Ok(())
 }
 
+/// Directory that contains the launcher executable. Used as the default
+/// external game-directory root for the one-click StarLight install flow.
+#[tauri::command]
+fn get_launcher_root_dir() -> api::Result<String> {
+    let exe = std::env::current_exe().map_err(|error| {
+        theseus::Error::from(theseus::ErrorKind::FSError(error.to_string()))
+    })?;
+    let dir = exe.parent().ok_or_else(|| {
+        theseus::Error::from(theseus::ErrorKind::FSError(
+            "Launcher executable has no parent directory".to_string(),
+        ))
+    })?;
+    Ok(dir.to_string_lossy().into_owned())
+}
+
 #[tauri::command]
 fn get_update_channel(app: tauri::AppHandle) -> api::Result<String> {
     let channel = read_update_channel_state(&app)?
@@ -838,6 +853,7 @@ fn main() {
         .manage(PendingUpdateData::default())
         .invoke_handler(tauri::generate_handler![
             initialize_state,
+            get_launcher_root_dir,
             get_update_channel,
             get_current_app_database_path,
             set_update_channel,