fix windows build

scripts/build-windows.ps1

@@ -5,6 +5,28 @@ param(
 Set-StrictMode -Version Latest
 $ErrorActionPreference = "Stop"
 
+function Assert-LastExitCode {
+    param(
+        [Parameter(Mandatory = $true)]
+        [string]$Step
+    )
+
+    if ($LASTEXITCODE -ne 0) {
+        if ($Step -eq "Frontend build") {
+            Write-Host ""
+            Write-Host "Frontend build failed, so desktop packaging was stopped on purpose." -ForegroundColor Yellow
+            Write-Host "This prevents packaging a stale frontend\\dist into the Windows app." -ForegroundColor Yellow
+            Write-Host ""
+            Write-Host "Next checks:" -ForegroundColor Yellow
+            Write-Host "  1. Run: npm run build" -ForegroundColor Yellow
+            Write-Host "  2. If you see 'spawn EPERM', try Node 20 LTS instead of Node 24." -ForegroundColor Yellow
+            Write-Host "  3. Reinstall frontend deps on Windows: npm --prefix frontend install" -ForegroundColor Yellow
+            Write-Host ""
+        }
+        throw "$Step failed with exit code $LASTEXITCODE."
+    }
+}
+
 $repoRoot = Split-Path -Parent $PSScriptRoot
 Set-Location $repoRoot
 
@@ -18,9 +40,11 @@ $demoDir = Join-Path $repoRoot "demo"
 
 Write-Host "Building frontend bundle..."
 npm run build
+Assert-LastExitCode "Frontend build"
 
 Write-Host "Installing desktop build dependencies..."
 & $pythonExe -m pip install -e ".[desktop]"
+Assert-LastExitCode "Desktop dependency installation"
 
 $mode = if ($OneFile) { "--onefile" } else { "--onedir" }
 
@@ -40,11 +64,13 @@ $pyInstallerArgs = @(
     "--collect-all", "matplotlib",
     "--collect-all", "scipy",
     "--collect-all", "skimage",
-    "--collect-all", "webview"
+    "--collect-all", "webview",
+    "--icon", "../resources/icon.ico"
 )
 
 Write-Host "Packaging desktop app..."
 & $pythonExe @pyInstallerArgs
+Assert-LastExitCode "PyInstaller packaging"
 
 Write-Host "Desktop build complete."
 Write-Host "Output folder: $repoRoot\desktop-dist\argonode"