Add Tauri launcher with Svelte UI

- Accounts: panel login/sign-up, Microsoft device-code sign-in, offline
  play; tokens encrypted with a key kept in the OS credential store
- Home: instance rail, live server status, news feed, social links,
  Play button with download progress, speed and ETA
- Full settings: accounts, memory/resolution/after-launch behaviour,
  Java and GC presets, Minecraft keybind editor applied to options.txt,
  theme overrides, storage manager, self-update via GitHub releases
- Game console, crash dialog with hints, per-instance overrides
- Live admin branding (colours, fonts, backgrounds, custom CSS)
- Online install tests for vanilla/Fabric/Quilt/Forge/NeoForge (CI)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011ARcGWxLx21FwXJ3yfGriS

launcher/src-tauri/src/state.rs

@@ -0,0 +1,87 @@
+use crate::accounts::AccountsFile;
+use crate::secrets::Secrets;
+use crate::settings::Settings;
+use scopenet_core::msa::DeviceCode;
+use scopenet_core::Layout;
+use scopenet_shared::LauncherManifest;
+use std::path::PathBuf;
+use std::sync::{Mutex, RwLock};
+
+/// Values baked in at build time by CI (see `.github/workflows/release.yml`).
+pub mod build {
+    /// Default panel URL for this build.
+    pub const PANEL_URL: Option<&str> = option_env!("SCOPENET_PANEL_URL");
+    /// `owner/repo` used to check GitHub releases for updates.
+    pub const REPO: Option<&str> = option_env!("SCOPENET_REPO");
+    /// When set to "1", players can't change the panel URL.
+    pub const LOCK_PANEL: Option<&str> = option_env!("SCOPENET_LOCK_PANEL");
+
+    pub fn panel_locked() -> bool {
+        LOCK_PANEL == Some("1") && PANEL_URL.is_some_and(|u| !u.is_empty())
+    }
+}
+
+pub struct RunningGame {
+    pub instance_id: String,
+    pub kill: tokio::sync::oneshot::Sender<()>,
+}
+
+pub struct AppState {
+    pub data_dir: PathBuf,
+    pub layout: Layout,
+    pub http: reqwest::Client,
+    pub settings: RwLock<Settings>,
+    pub accounts: RwLock<AccountsFile>,
+    pub secrets: Secrets,
+    pub manifest: RwLock<Option<LauncherManifest>>,
+    pub device_code: Mutex<Option<DeviceCode>>,
+    pub ms_cancel: Mutex<Option<tokio::sync::oneshot::Sender<()>>>,
+    /// Install/launch pipeline in progress (abortable).
+    pub task: Mutex<Option<tokio::task::AbortHandle>>,
+    pub game: Mutex<Option<RunningGame>>,
+}
+
+impl AppState {
+    pub fn new(data_dir: PathBuf) -> Self {
+        std::fs::create_dir_all(&data_dir).ok();
+        let settings = Settings::load(&data_dir.join("settings.json"));
+        let accounts = AccountsFile::load(&data_dir.join("accounts.json"));
+        let manifest = std::fs::read(data_dir.join("manifest.json")).ok().and_then(|b| serde_json::from_slice(&b).ok());
+        Self {
+            layout: Layout::new(data_dir.join("minecraft")),
+            http: scopenet_core::http::client(),
+            secrets: Secrets::open(&data_dir),
+            settings: RwLock::new(settings),
+            accounts: RwLock::new(accounts),
+            manifest: RwLock::new(manifest),
+            device_code: Mutex::new(None),
+            ms_cancel: Mutex::new(None),
+            task: Mutex::new(None),
+            game: Mutex::new(None),
+            data_dir,
+        }
+    }
+
+    /// The panel this launcher talks to (baked-in when locked).
+    pub fn panel_url(&self) -> Option<String> {
+        let chosen = self.settings.read().unwrap().panel_url.clone().filter(|u| !u.is_empty());
+        let baked = build::PANEL_URL.filter(|u| !u.is_empty()).map(String::from);
+        let url = if build::panel_locked() { baked } else { chosen.or(baked) };
+        url.map(|u| u.trim_end_matches('/').to_string())
+    }
+
+    pub fn save_settings(&self) -> anyhow::Result<()> {
+        self.settings.read().unwrap().save(&self.data_dir.join("settings.json"))
+    }
+
+    pub fn save_accounts(&self) -> anyhow::Result<()> {
+        self.accounts.read().unwrap().save(&self.data_dir.join("accounts.json"))
+    }
+
+    pub fn cache_manifest(&self, m: &LauncherManifest) {
+        *self.manifest.write().unwrap() = Some(m.clone());
+        if let Ok(bytes) = serde_json::to_vec(m) {
+            std::fs::write(self.data_dir.join("manifest.json"), bytes).ok();
+        }
+    }
+}