Add extension filtering to install scripts

Both scripts now accept optional extension names as arguments:
  ./install-extensions.sh ado-build-watcher
  .\install-extensions.ps1 ado-pr-watcher

With no arguments, all extensions are installed (existing behavior).
Invalid names produce a warning with available options.
Shared lib/ is always installed regardless of filter.

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

Author: cirvine-MSFT

README.md

@@ -64,6 +64,13 @@ cd copilot-toolkit
 ./install-extensions.sh
 ```
 
+To install only specific extensions:
+
+```bash
+./install-extensions.sh ado-build-watcher          # just the build watcher
+.\install-extensions.ps1 ado-pr-watcher             # just the PR watcher
+```
+
 After installing, run `/clear` in the Copilot CLI or restart it to load the new extensions.
 
 ### Update

install-extensions.ps1

@@ -1,5 +1,15 @@
 # install-extensions.ps1 — Install Copilot CLI extensions from this repo
 # Works on Windows PowerShell 5.1+ and pwsh 7+
+#
+# Usage:
+#   .\install-extensions.ps1                      # Install all extensions
+#   .\install-extensions.ps1 ado-build-watcher    # Install only ado-build-watcher
+#   .\install-extensions.ps1 ado-pr-watcher ado-build-watcher  # Install specific ones
+
+param(
+    [Parameter(ValueFromRemainingArguments)]
+    [string[]]$Only
+)
 
 $ErrorActionPreference = "Stop"
 
@@ -18,7 +28,20 @@ if (-not (Test-Path $sourceDir)) {
     exit 1
 }
 
-$extensions = @("ado-pr-watcher", "ado-build-watcher")
+$allExtensions = @("ado-pr-watcher", "ado-build-watcher")
+if ($Only -and $Only.Count -gt 0) {
+    $extensions = @($Only | Where-Object { $allExtensions -contains $_ })
+    $invalid = @($Only | Where-Object { $allExtensions -notcontains $_ })
+    if ($invalid.Count -gt 0) {
+        Write-Warning "Unknown extension(s): $($invalid -join ', '). Available: $($allExtensions -join ', ')"
+    }
+    if ($extensions.Count -eq 0) {
+        Write-Error "No valid extensions specified."
+        exit 1
+    }
+} else {
+    $extensions = $allExtensions
+}
 $sharedDirs = @("lib")
 [string[]]$installed = @()
 

install-extensions.sh

@@ -1,6 +1,11 @@
 #!/usr/bin/env bash
 # install-extensions.sh — Install Copilot CLI extensions from this repo
 # Works on macOS and Linux
+#
+# Usage:
+#   ./install-extensions.sh                      # Install all extensions
+#   ./install-extensions.sh ado-build-watcher    # Install only ado-build-watcher
+#   ./install-extensions.sh ado-pr-watcher ado-build-watcher  # Install specific ones
 
 set -euo pipefail
 
@@ -16,7 +21,29 @@ if [ ! -d "$SOURCE_DIR" ]; then
     exit 1
 fi
 
-EXTENSIONS=("ado-pr-watcher" "ado-build-watcher")
+ALL_EXTENSIONS=("ado-pr-watcher" "ado-build-watcher")
+
+if [ $# -gt 0 ]; then
+    EXTENSIONS=()
+    for arg in "$@"; do
+        found=0
+        for valid in "${ALL_EXTENSIONS[@]}"; do
+            if [ "$arg" = "$valid" ]; then found=1; break; fi
+        done
+        if [ "$found" -eq 1 ]; then
+            EXTENSIONS+=("$arg")
+        else
+            echo "Warning: Unknown extension '$arg'. Available: ${ALL_EXTENSIONS[*]}"
+        fi
+    done
+    if [ ${#EXTENSIONS[@]} -eq 0 ]; then
+        echo "Error: No valid extensions specified." >&2
+        exit 1
+    fi
+else
+    EXTENSIONS=("${ALL_EXTENSIONS[@]}")
+fi
+
 SHARED_DIRS=("lib")
 INSTALLED=()