chore: add electron install location identifier apis for auto updater

src-electron/main.js

@@ -253,12 +253,28 @@ ipcMain.handle('is-packaged', (event) => {
     return app.isPackaged;
 });
 
-// Get executable path (path to the AppImage on Linux)
+// Path to the running Electron binary. On Linux AppImages this is the
+// FUSE-mounted binary (/tmp/.mount_*/...), not the .AppImage file —
+// use 'get-installed-app-path' if you need the user-visible install path.
 ipcMain.handle('get-executable-path', (event) => {
     assertTrusted(event);
     return process.execPath;
 });
 
+// Path of the installed app, or null if not running from an installed build.
+// - Linux AppImage: process.env.APPIMAGE (set by AppRun to the .AppImage path)
+// - Other / dev / unpacked: null (auto-update not supported yet)
+ipcMain.handle('get-installed-app-path', (event) => {
+    assertTrusted(event);
+    if (!app.isPackaged) {
+        return null;
+    }
+    if (process.platform === 'linux') {
+        return process.env.APPIMAGE || null;
+    }
+    return null;
+});
+
 // Update scheduled state - shared across windows for multi-window update persistence
 ipcMain.handle('set-update-scheduled', (event, scheduled) => {
     assertTrusted(event);

src-electron/preload.js

@@ -173,6 +173,7 @@ contextBridge.exposeInMainWorld('electronAPI', {
     getAppVersion: () => ipcRenderer.invoke('get-app-version'),
     isPackaged: () => ipcRenderer.invoke('is-packaged'),
     getExecutablePath: () => ipcRenderer.invoke('get-executable-path'),
+    getInstalledAppPath: () => ipcRenderer.invoke('get-installed-app-path'),
     setUpdateScheduled: (scheduled) => ipcRenderer.invoke('set-update-scheduled', scheduled),
     getUpdateScheduled: () => ipcRenderer.invoke('get-update-scheduled')
 });