Fix PS 5.1 compat: robust copy, typed arrays, no ternary

- Replace Copy-Item glob with Get-ChildItem pipe (more reliable in PS 5.1)
- Use [string[]] typed arrays for  and
- Replace ternary-style if expression with if/else block (PS 5.1 compat)
- Replace em-dash with ASCII dash in warnings (encoding safety)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: cirvine-MSFT

install-extensions.ps1

@@ -6,7 +6,11 @@ $ErrorActionPreference = "Stop"
 $repoRoot = $PSScriptRoot
 $sourceDir = Join-Path $repoRoot "extensions"
 # Respect COPILOT_HOME if set (same env var the Copilot CLI uses)
-$copilotHome = if ($env:COPILOT_HOME) { $env:COPILOT_HOME } else { Join-Path $HOME ".copilot" }
+if ($env:COPILOT_HOME) {
+    $copilotHome = $env:COPILOT_HOME
+} else {
+    $copilotHome = Join-Path $HOME ".copilot"
+}
 $targetDir = Join-Path $copilotHome "extensions"
 
 if (-not (Test-Path $sourceDir)) {
@@ -16,37 +20,37 @@ if (-not (Test-Path $sourceDir)) {
 
 $extensions = @("ado-pr-watcher", "ado-build-watcher")
 $sharedDirs = @("lib")
-$installed = @()
+[string[]]$installed = @()
 
 foreach ($ext in $extensions) {
     $src = Join-Path $sourceDir $ext
     $dst = Join-Path $targetDir $ext
     if (-not (Test-Path $src)) {
-        Write-Warning "Skipping '$ext' — source not found at '$src'"
+        Write-Warning "Skipping '$ext' - source not found at '$src'"
         continue
     }
     # Clean target first so stale files from previous versions are removed
     if (Test-Path $dst) { Remove-Item $dst -Recurse -Force }
     New-Item -ItemType Directory -Path $dst -Force | Out-Null
-    Copy-Item (Join-Path $src "*") $dst -Force -Recurse
-    $installed += $ext
+    Get-ChildItem $src | Copy-Item -Destination $dst -Recurse -Force
+    $installed += [string]$ext
 }
 
 foreach ($dir in $sharedDirs) {
     $src = Join-Path $sourceDir $dir
     $dst = Join-Path $targetDir $dir
     if (-not (Test-Path $src)) {
-        Write-Warning "Skipping shared dir '$dir' — source not found at '$src'"
+        Write-Warning "Skipping shared dir '$dir' - source not found at '$src'"
         continue
     }
     if (Test-Path $dst) { Remove-Item $dst -Recurse -Force }
     New-Item -ItemType Directory -Path $dst -Force | Out-Null
-    Copy-Item (Join-Path $src "*") $dst -Force -Recurse
-    $installed += $dir
+    Get-ChildItem $src | Copy-Item -Destination $dst -Recurse -Force
+    $installed += [string]$dir
 }
 
 # Preflight warnings
-$missingTools = @()
+[string[]]$missingTools = @()
 if (-not (Get-Command copilot -ErrorAction SilentlyContinue)) { $missingTools += "copilot (GitHub Copilot CLI)" }
 if (-not (Get-Command az -ErrorAction SilentlyContinue)) { $missingTools += "az (Azure CLI)" }