feat(runtime): prepare safe context checkpoints

scripts/windows-smoke.ps1

@@ -183,6 +183,91 @@ function Assert-TemporaryChildWithoutReparsePoint {
     return $target
 }
 
+function Import-VisualStudioBuildEnvironment {
+    $originalPath = $env:Path
+    $programFilesX86 = [Environment]::GetFolderPath(
+        [Environment+SpecialFolder]::ProgramFilesX86
+    )
+    $vswherePath = Join-Path `
+        -Path $programFilesX86 `
+        -ChildPath "Microsoft Visual Studio\Installer\vswhere.exe"
+    if (-not (Test-Path -LiteralPath $vswherePath -PathType Leaf)) {
+        throw "Visual Studio Installer's vswhere.exe was not found. Install Microsoft C++ Build Tools."
+    }
+
+    $installationPath = (
+        & $vswherePath `
+            -latest `
+            -products "*" `
+            -requires "Microsoft.VisualStudio.Component.VC.Tools.x86.x64" `
+            -property installationPath
+    ).Trim()
+    if ($LASTEXITCODE -ne 0 -or [string]::IsNullOrWhiteSpace($installationPath)) {
+        throw "Microsoft C++ Build Tools were not found."
+    }
+
+    $devCommandPath = Join-Path `
+        -Path $installationPath `
+        -ChildPath "Common7\Tools\VsDevCmd.bat"
+    if (-not (Test-Path -LiteralPath $devCommandPath -PathType Leaf)) {
+        throw "VsDevCmd.bat was not found in the selected Visual Studio installation."
+    }
+
+    $commandLine = 'call "' + $devCommandPath + '" -arch=x64 -host_arch=x64 >nul && set'
+    $environmentLines = @(& $env:ComSpec /d /c $commandLine)
+    if ($LASTEXITCODE -ne 0) {
+        throw "Visual Studio x64 developer environment initialization failed."
+    }
+
+    $developerPath = $null
+    foreach ($line in $environmentLines) {
+        $separator = $line.IndexOf("=")
+        if ($separator -le 0) {
+            continue
+        }
+        if ($line.StartsWith("PATH=", [System.StringComparison]::Ordinal)) {
+            $developerPath = $line.Substring($separator + 1)
+            continue
+        }
+        [Environment]::SetEnvironmentVariable(
+            $line.Substring(0, $separator),
+            $line.Substring($separator + 1),
+            "Process"
+        )
+    }
+    if ([string]::IsNullOrWhiteSpace($developerPath)) {
+        throw "Visual Studio did not publish a developer PATH."
+    }
+    $pathSegments = @($developerPath)
+    $userProfilePath = $env:USERPROFILE
+    if ([string]::IsNullOrWhiteSpace($userProfilePath)) {
+        $userProfilePath = [Environment]::GetFolderPath(
+            [Environment+SpecialFolder]::UserProfile
+        )
+    }
+    $cargoBinPath = Join-Path `
+        -Path $userProfilePath `
+        -ChildPath ".cargo\bin"
+    if (Test-Path -LiteralPath (Join-Path -Path $cargoBinPath -ChildPath "rustup.exe") -PathType Leaf) {
+        $pathSegments += $cargoBinPath
+    }
+    $pathSegments += $originalPath
+    $env:Path = $pathSegments -join [System.IO.Path]::PathSeparator
+
+    foreach ($requiredTool in @("cl.exe", "link.exe", "rc.exe")) {
+        $tool = Get-Command `
+            -Name $requiredTool `
+            -CommandType Application `
+            -ErrorAction SilentlyContinue |
+            Select-Object -First 1
+        if ($null -eq $tool) {
+            throw "$requiredTool was not found after loading Visual Studio Build Tools and the Windows SDK."
+        }
+    }
+
+    Write-Host ("[ok] Visual Studio x64 C++ Build Tools and Windows SDK from {0}" -f $installationPath)
+}
+
 if ($Demo -and -not $Launch) {
     throw "-Demo is only valid together with -Launch."
 }
@@ -193,6 +278,8 @@ if (-not $Launch -and -not [string]::IsNullOrWhiteSpace($SmokeDataPath)) {
     throw "-SmokeDataPath is only valid together with -Launch."
 }
 
+Import-VisualStudioBuildEnvironment
+
 $projectRoot = [System.IO.Path]::GetFullPath((Join-Path -Path $PSScriptRoot -ChildPath ".."))
 $packageJsonPath = Join-Path -Path $projectRoot -ChildPath "package.json"
 $lappLockPath = Join-Path -Path $projectRoot -ChildPath "lapp-rs.lock"
@@ -372,8 +459,9 @@ if (-not [string]::IsNullOrWhiteSpace($lappWorkTreeStatus)) {
 }
 Write-Host ("[ok] lapp-rs matches {0}" -f $expectedLappCommit.Substring(0, 12))
 
-# Keep all automated gates deterministic and noninteractive. No environment
-# variables are enumerated or printed.
+# Keep all automated gates deterministic and noninteractive. Visual Studio's
+# developer shell is imported into this process; environment values are never
+# printed or persisted by this script.
 $env:CI = "true"
 $env:NO_COLOR = "1"
 $env:CARGO_TERM_COLOR = "never"