fix(test): guard npm module path lookup when HOME is unset

Windows CI runners often lack HOME, which made Join-Path throw inside
Get-TestNodeModuleSearchPaths and fail binary conversion integration
tests before they could skip missing npm packages. Fall back to
USERPROFILE and skip null base paths instead.

Co-authored-by: Michael Bolens <bolens@users.noreply.github.com>

Author: cursoragent

tests/TestSupport/TestNpmHelpers.ps1

@@ -39,10 +39,20 @@ function Get-TestNodeModuleSearchPaths {
         }
     }
 
-    foreach ($candidate in @(
-            "$env:LOCALAPPDATA\pnpm\global\5\node_modules"
-            (Join-Path $env:HOME '.local/share/pnpm/global/5/node_modules')
-        )) {
+    $fallbackCandidates = @()
+    if ($env:LOCALAPPDATA) {
+        $fallbackCandidates += Join-Path $env:LOCALAPPDATA 'pnpm\global\5\node_modules'
+    }
+
+    $homeDirectory = $env:HOME
+    if ([string]::IsNullOrWhiteSpace($homeDirectory)) {
+        $homeDirectory = $env:USERPROFILE
+    }
+    if (-not [string]::IsNullOrWhiteSpace($homeDirectory)) {
+        $fallbackCandidates += Join-Path $homeDirectory '.local/share/pnpm/global/5/node_modules'
+    }
+
+    foreach ($candidate in $fallbackCandidates) {
         if ($candidate -and (Test-Path -LiteralPath $candidate)) {
             $paths.Add($candidate)
         }
@@ -73,6 +83,10 @@ function Get-TestNodeModuleSearchPaths {
     }
 
     foreach ($repoRoot in @($repoRoots | Select-Object -Unique)) {
+        if ([string]::IsNullOrWhiteSpace($repoRoot)) {
+            continue
+        }
+
         $localModules = Join-Path $repoRoot 'node_modules'
         if (Test-Path -LiteralPath $localModules) {
             $paths.Add($localModules)

tests/unit/test-support/test-support.tests.ps1

@@ -418,6 +418,24 @@ Describe 'TestSupport Modules' {
     }
 
     Describe 'TestNpmHelpers Module' {
+        Context 'Get-TestNodeModuleSearchPaths' {
+            It 'Does not throw when HOME is unset on Windows-style environments' {
+                $originalHome = $env:HOME
+                try {
+                    Remove-Item Env:HOME -ErrorAction SilentlyContinue
+                    { $null = Get-TestNodeModuleSearchPaths } | Should -Not -Throw
+                }
+                finally {
+                    if ($null -ne $originalHome) {
+                        $env:HOME = $originalHome
+                    }
+                    else {
+                        Remove-Item Env:HOME -ErrorAction SilentlyContinue
+                    }
+                }
+            }
+        }
+
         Context 'Test-NpmPackageAvailable' {
             It 'Returns false when package is not available' {
                 if (-not (Get-Command node -ErrorAction SilentlyContinue)) {