fix(desktop): match VS Code Linux sandbox handling, scope --no-sandbox to AppImage

The Linux wrapper renamed the executable to Paseo.bin and exec'd it with
--no-sandbox, which surfaced as Paseo.bin in the dock and process list on
Ubuntu. Drop the wrapper and the chrome-sandbox deletion entirely. .deb/.rpm
now ship chrome-sandbox SUID 4755 (electron-builder 26 default postinst,
matches VS Code) and run Paseo directly with the Chromium sandbox on.
AppImage cannot carry SUID, so --no-sandbox is now injected at runtime only
when process.env.APPIMAGE is set.

Fixes #602
Re #381

packages/desktop/src/main.ts

@@ -86,6 +86,13 @@ if (forcedUserDataDir) {
   }
 }
 
+// AppImage runtimes mount the app from /tmp under the user's UID, so the SUID
+// chrome-sandbox helper we ship in .deb/.rpm cannot work there. Disable the
+// sandbox only in that case; .deb/.rpm keep the sandbox on, matching VS Code.
+if (process.platform === "linux" && process.env.APPIMAGE) {
+  app.commandLine.appendSwitch("no-sandbox");
+}
+
 // Allow users to pass Chromium flags via PASEO_ELECTRON_FLAGS for debugging
 // rendering issues (e.g. "--disable-gpu --ozone-platform=x11").
 // Must run before app.whenReady().