Ship Windows plug-and-play host exe with USB wait and autostart.

Users no longer need Python: run.bat or install_autostart.ps1; agent reconnects when CYD is plugged in.

host/build_exe.ps1

@@ -0,0 +1,34 @@
+# Build a standalone Windows exe (no Python install needed on target PCs).
+# Output: host\dist\send_sysinfo.exe
+
+$ErrorActionPreference = "Stop"
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+Set-Location $here
+
+$pyCandidates = @(
+  "python",
+  (Join-Path $env:USERPROFILE "AppData\Local\Programs\Python\Python312\python.exe"),
+  (Join-Path $env:USERPROFILE "AppData\Local\Programs\Python\Python311\python.exe")
+)
+$py = $null
+foreach ($c in $pyCandidates) {
+  $cmd = Get-Command $c -ErrorAction SilentlyContinue
+  if ($cmd) { $py = $cmd.Source; break }
+  if (Test-Path $c) { $py = $c; break }
+}
+if (-not $py) { throw "Python required only on the build machine." }
+
+& $py -m pip install -q pyinstaller psutil pyserial nvidia-ml-py
+& $py -m PyInstaller --noconfirm --clean --onefile --console `
+  --name send_sysinfo `
+  --hidden-import serial.tools.list_ports `
+  --hidden-import psutil `
+  --collect-all nvidia_ml_py `
+  .\send_sysinfo.py
+
+if (-not (Test-Path ".\dist\send_sysinfo.exe")) {
+  throw "Build failed: dist\send_sysinfo.exe missing"
+}
+Copy-Item ".\dist\send_sysinfo.exe" ".\send_sysinfo.exe" -Force
+Write-Host "OK -> $here\send_sysinfo.exe"
+Write-Host "Also -> $here\dist\send_sysinfo.exe"