Fix Python 3.11 detection in the Windows build script

sys.version_info[:2] prints '(3, 11)', so the old substring check for '3.11' always failed even on a valid Python install. Probe the major.minor string explicitly and support the py launcher or python on PATH.

Co-Authored-By: Claude Code <noreply@anthropic.com>

build_windows.ps1

@@ -10,15 +10,19 @@ $Root = Split-Path -Parent $MyInvocation.MyCommand.Path
 Set-Location $Root
 
 function Get-Python {
-    $candidates = @("py -3.11", "py -3", "python")
+    $candidates = @(
+        @{ Command = "py"; Arguments = @("-3.11") },
+        @{ Command = "py"; Arguments = @("-3") },
+        @{ Command = "python"; Arguments = @() },
+        @{ Command = "python3"; Arguments = @() }
+    )
     foreach ($candidate in $candidates) {
         try {
-            $parts = $candidate.Split(" ")
-            $exe = $parts[0]
-            $exeArgs = @($parts | Select-Object -Skip 1)
-            $output = & $exe @exeArgs -c "import sys; print(sys.executable); print(sys.version_info[:2])" 2>$null
-            if ($LASTEXITCODE -eq 0 -and $output -match "3\.11") {
-                return $parts
+            $exe = $candidate.Command
+            $exeArgs = @($candidate.Arguments)
+            $probe = & $exe @exeArgs -c "import sys; print('{0}.{1}'.format(sys.version_info[0], sys.version_info[1]))" 2>$null
+            if ($LASTEXITCODE -eq 0 -and (($probe | Out-String).Trim() -eq "3.11")) {
+                return $candidate
             }
         } catch { }
     }
@@ -31,8 +35,8 @@ $python = Get-Python
 
 if (-not (Test-Path $venv)) {
     Write-Host "Creating build environment..."
-    $pythonExe = $python[0]
-    $pythonArgs = @($python | Select-Object -Skip 1)
+    $pythonExe = $python.Command
+    $pythonArgs = @($python.Arguments)
     & $pythonExe @pythonArgs -m venv $venv
 }
 $py = Join-Path $venv "Scripts\python.exe"