Package game as Electron desktop app

Custom app:// privileged protocol (standard, secure, fetch, stream) serves
the game so absolute /assets/ fetches and streamed mp3 loops work without
game code changes. Borderless windowed fullscreen, F11/F12/Ctrl+R/Ctrl+Shift+I
accelerators, single-instance lock, and an opt-in MS_VERIFY harness that
drives a run and dumps asset/audio diagnostics.

Pinned electron@40.10.2 + electron-builder@25.1.8 for Node 20 compatibility.
Builder allowlist ships only runtime content and excludes assets/raw.

electron-builder.yml

@@ -0,0 +1,16 @@
+appId: com.meatslicer.game
+productName: MeatSlicer
+asar: false
+files:
+  - "desktop/**"
+  - "index.html"
+  - "css/**"
+  - "js/**"
+  - "assets/**"
+  - "!assets/raw/**"
+  - "mp3-music/**"
+  - "package.json"
+win:
+  target:
+    - zip
+  icon: build/icon.png