feat(ci): use patched Linux Electron from GitHub release

Rewrite download-electron.js to download both Windows (v42) and
Linux (v43) patched binaries from bigjakk/Electron-Websocket-Fix,
matching KPC's multi-platform approach. On CI, binaries go to
dist-win/ and dist-linux/; locally the current platform replaces
dist/. Both platforms now use the patched Electron.

.github/workflows/build-release.yml

@@ -56,18 +56,6 @@ jobs:
         if: steps.version-check.outputs.SKIP == 'false'
         run: npm ci --legacy-peer-deps
 
-      - name: Ensure Electron Linux binary
-        if: steps.version-check.outputs.SKIP == 'false'
-        run: |
-          if [ ! -f node_modules/electron/dist/electron ]; then
-            echo "Electron Linux binary not found in dist/, triggering download..."
-            node node_modules/electron/install.js
-          fi
-          echo "=== Electron binaries ==="
-          echo "dist/electron: $(ls -lh node_modules/electron/dist/electron 2>/dev/null || echo MISSING)"
-          echo "dist-win/electron.exe: $(ls -lh node_modules/electron/dist-win/electron.exe 2>/dev/null || echo MISSING)"
-          echo "path.txt: $(cat node_modules/electron/path.txt 2>/dev/null || echo MISSING)"
-
       - name: Build source
         if: steps.version-check.outputs.SKIP == 'false'
         run: npm run build
@@ -80,7 +68,7 @@ jobs:
 
       - name: Build Linux distributables
         if: steps.version-check.outputs.SKIP == 'false'
-        run: npx electron-builder --linux -c.electronDist=node_modules/electron/dist --publish never
+        run: npx electron-builder --linux -c.electronDist=node_modules/electron/dist-linux --publish never
 
       - name: Report build sizes
         if: steps.version-check.outputs.SKIP == 'false'