fix(desktop): download target Electron for cross-platform packaging

apps/desktop/scripts/run-electron-builder.mjs

@@ -36,7 +36,18 @@ function electronBuilderCli() {
   return path.join(path.dirname(pkgJson), rel)
 }
 
-const dist = electronDistDir()
+const cliArgs = process.argv.slice(2)
+// An installed Electron dist belongs to the host. Cross-platform packaging
+// must download the requested target instead of copying the host executable.
+const crossPlatform =
+  (cliArgs.includes('--win') && process.platform !== 'win32') ||
+  (cliArgs.includes('--mac') && process.platform !== 'darwin') ||
+  (cliArgs.includes('--linux') && process.platform !== 'linux')
+const crossArch =
+  (cliArgs.includes('--x64') && process.arch !== 'x64') ||
+  (cliArgs.includes('--arm64') && process.arch !== 'arm64') ||
+  (cliArgs.includes('--ia32') && process.arch !== 'ia32')
+const dist = crossPlatform || crossArch ? null : electronDistDir()
 // Local `hermes desktop` builds only ever package (--dir or dist), never
 // publish a GitHub release — no CI workflow drives this script. But the npm
 // lifecycle env sets CI=1 (so esbuild's postinstall doesn't try interactive
@@ -55,7 +66,7 @@ if (dist && fs.existsSync(distBinary(dist))) {
       "via @electron/get (electronVersion + ELECTRON_MIRROR)."
   )
 }
-args.push(...process.argv.slice(2))
+args.push(...cliArgs)
 
 const result = spawnSync(process.execPath, [electronBuilderCli(), ...args], {
   stdio: "inherit",