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.

.gitignore

@@ -1,6 +1,8 @@
 tools/.env
 tools/.venv/
 assets/raw/
+node_modules/
+dist/
 .playwright-mcp/
 .serena/
 served-state.txt