fix(ci): ensure Linux electron binary, pass electronDist per-platform

electron-nightly may not auto-download the Linux binary on CI.
Add explicit step to trigger download if missing. Pass electronDist
as CLI override per-platform (dist-win for Windows, dist for Linux)
instead of in config. Write path.txt on all platforms like KPC.

scripts/download-electron.js

@@ -151,11 +151,8 @@ async function main() {
 
     // Write path.txt so the electron package's lazy downloader (index.js)
     // considers the binary already installed and doesn't re-download stock.
-    // On non-Windows (CI cross-compilation), skip this so electron-nightly still
-    // downloads the native Linux binary into dist/ for the Linux build target.
-    if (IS_WIN) {
-        fs.writeFileSync(path.join(ELECTRON_DIST, '..', 'path.txt'), 'electron.exe');
-    }
+    const platformExe = IS_WIN ? 'electron.exe' : 'electron';
+    fs.writeFileSync(path.join(ELECTRON_DIST, '..', 'path.txt'), platformExe);
 
     // Write marker and verify
     if (fs.existsSync(VERSION_FILE)) {