build: add automated WiX extraction script for Windows builds

- Create scripts/build-windows.js that extracts wix314-binaries.zip to tools/wix314/
- Adds extracted dir to PATH so electron-wix-msi can find candle.exe/light.exe
- Adds npm script 'make:win' for one-command Windows installer build

scripts/build-windows.js

@@ -0,0 +1,50 @@
+const { execSync, spawn } = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+const WIX_ZIP = path.join(process.cwd(), 'wix314-binaries.zip');
+const WIX_DIR = path.join(process.cwd(), 'tools', 'wix314');
+
+function extractWix() {
+  if (!fs.existsSync(WIX_ZIP)) {
+    console.error(`WiX zip not found: ${WIX_ZIP}`);
+    process.exit(1);
+  }
+
+  if (fs.existsSync(WIX_DIR)) {
+    console.log(`WiX already extracted at ${WIX_DIR}`);
+    return;
+  }
+
+  console.log(`Extracting WiX binaries to ${WIX_DIR}...`);
+  fs.mkdirSync(WIX_DIR, { recursive: true });
+
+  // Use PowerShell Expand-Archive (built into Windows)
+  const psCommand = `Expand-Archive -Path "${WIX_ZIP}" -DestinationPath "${WIX_DIR}" -Force`;
+  execSync(psCommand, { shell: 'powershell.exe', stdio: 'inherit' });
+
+  console.log('WiX extraction complete.');
+}
+
+function setupWixPath() {
+  // electron-wix-msi's detect-wix.js runs execSync('candle -?') which relies on PATH
+  process.env.PATH = `${WIX_DIR};${process.env.PATH}`;
+  console.log(`Added ${WIX_DIR} to PATH`);
+}
+
+function runMake() {
+  console.log('Running electron-forge make...');
+  const make = spawn('npx', ['electron-forge', 'make'], {
+    stdio: 'inherit',
+    shell: true,
+    env: process.env,
+  });
+
+  make.on('exit', (code) => {
+    process.exit(code ?? 0);
+  });
+}
+
+extractWix();
+setupWixPath();
+runMake();