fix(capabilities): read Python exit code directly

scripts/commands/check-capabilities.ps1

@@ -13,8 +13,9 @@ Require-Command jq
 $pythonVersion = $null
 foreach ($python in @('python', 'python3')) {
     if (-not (Get-Command $python -ErrorAction SilentlyContinue)) { continue }
-    $candidate = (& $python --version 2>$null | Select-Object -First 1) -replace '^Python\s+', ''
+    $candidate = & $python --version 2>$null
-    if ($LASTEXITCODE -eq 0) { $pythonVersion = $candidate; break }
+    $pythonExitCode = $LASTEXITCODE
+    if ($pythonExitCode -eq 0) { $pythonVersion = $candidate -replace '^Python\s+', ''; break }
 }
 if ($null -ne $pythonVersion) { Check-Version 'Python' $pythonVersion ([version]'3.11') } else { Fail 'Python 3.11 or newer is required' }
 

scripts/tests/test-capabilities.ps1

@@ -0,0 +1,11 @@
+[CmdletBinding()]
+param([switch]$Summary)
+$ErrorActionPreference = 'Stop'
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+$content = Get-Content (Join-Path $root 'scripts/commands/check-capabilities.ps1') -Raw
+
+if ($content -match '(?s)\(& \$python --version.*?Select-Object.*?\).*?\$LASTEXITCODE') {
+    throw 'Python capability detection must not read $LASTEXITCODE after a pipeline.'
+}
+
+if ($Summary) { Write-Output 'Tests: PASS | capabilities' } else { Write-Output 'PASS capabilities: Python exit code is read without a pipeline' }