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.

electron-builder.yml

@@ -1,6 +1,5 @@
 appId: com.krunkercivilian.client
 productName: Krunker Civilian Client
-electronDist: node_modules/electron/dist
 directories:
   output: out
   buildResources: build