Install Copilot CLI into the agent tool cache (ADR §10093)

Replace the prior `npm install -g` (which puts the binary on the global PATH but
not in the agent tool cache) with a tool-cache install at
$AGENT_TOOLSDIRECTORY/copilot-cli/<version>/x64/ plus the matching
`x64.complete` marker. This matches the layout that the runtime resolver
in gh-aw-actions/setup expects from `tc.find("copilot-cli", ...)`, so
hosted runner jobs hit a warm cache instead of re-installing the CLI on
every run.

Mirrors the conventions already used by install-awf.sh and
install-codeql-bundle.sh in the same directory. Updates the Pester test
to validate the tool-cache layout (directory, bin/copilot, and .complete
marker) in Tools.Tests.ps1, mirroring the existing AWF block, and drops
the now-stale `copilot --version` check from CLI.Tools.Tests.ps1 since
PATH augmentation is handled at runtime by the setup action, not by the
bake.

Author: salmanmkc

images/ubuntu/scripts/build/install-copilot-cli.sh

@@ -48,7 +48,21 @@ if ! [[ "$copilot_version" =~ ^[0-9]+\.[0-9]+\.[0-9]+(-[0-9A-Za-z.-]+)?$ ]]; the
     exit 1
 fi
 
-echo "Installing GitHub Copilot CLI v$copilot_version (pinned via compat.json)..."
-npm install -g "@github/copilot@${copilot_version}" --ignore-scripts
+# Install into the agent tool cache so the gh-aw-actions/setup action's
+# tc.find("copilot-cli", ...) lookup succeeds on hosted runners. Layout:
+#   $AGENT_TOOLSDIRECTORY/copilot-cli/<version>/x64/{bin,lib}
+#   $AGENT_TOOLSDIRECTORY/copilot-cli/<version>/x64.complete
+# Mirrors the conventions used by install-awf.sh and install-codeql-bundle.sh
+# and matches the layout the runtime resolver expects (see ADR
+# https://github.com/github/c2c-actions/blob/main/docs/adrs/10093-copilot-cli-stability-for-agentic-workflows.md).
+copilot_toolcache_path="$AGENT_TOOLSDIRECTORY/copilot-cli/$copilot_version/x64"
+mkdir -p "$copilot_toolcache_path"
 
-invoke_tests "CLI.Tools" "Copilot CLI"
+echo "Installing GitHub Copilot CLI v$copilot_version into $copilot_toolcache_path (pinned via compat.json)..."
+npm install -g --prefix "$copilot_toolcache_path" \
+    "@github/copilot@${copilot_version}" --ignore-scripts
+
+# Mark the tool-cache entry complete so @actions/tool-cache#find returns it.
+touch "$copilot_toolcache_path.complete"
+
+invoke_tests "Tools" "Copilot CLI"

images/ubuntu/scripts/tests/CLI.Tools.Tests.ps1

@@ -36,12 +36,6 @@ Describe "GitHub CLI" {
     }
 }
 
-Describe "Copilot CLI" -Skip:(Test-IsUbuntu22) {
-    It "copilot cli" {
-        "copilot --version" | Should -ReturnZeroExitCode
-    }
-}
-
 Describe "Google Cloud CLI" {
     It "Google Cloud CLI" {
         "gcloud --version" | Should -ReturnZeroExitCode

images/ubuntu/scripts/tests/Tools.Tests.ps1

@@ -428,3 +428,24 @@ Describe "AWF" -Skip:(Test-IsUbuntu22) {
         $bundlePath | Should -Exist
     }
 }
+
+Describe "Copilot CLI" -Skip:(Test-IsUbuntu22) {
+    It "Copilot CLI toolcache directory exists" {
+        $copilotPath = Join-Path $env:AGENT_TOOLSDIRECTORY "copilot-cli"
+        $copilotPath | Should -Exist
+    }
+
+    It "Copilot CLI binary exists in toolcache" {
+        $copilotPath = Join-Path $env:AGENT_TOOLSDIRECTORY "copilot-cli"
+        $latestVersion = Get-ChildItem -Path $copilotPath -Directory | Sort-Object -Property { [version]$_.Name } -Descending | Select-Object -First 1
+        $binPath = Join-Path $latestVersion.FullName "x64" "bin" "copilot"
+        $binPath | Should -Exist
+    }
+
+    It "Copilot CLI toolcache .complete marker exists" {
+        $copilotPath = Join-Path $env:AGENT_TOOLSDIRECTORY "copilot-cli"
+        $latestVersion = Get-ChildItem -Path $copilotPath -Directory | Sort-Object -Property { [version]$_.Name } -Descending | Select-Object -First 1
+        $completeMarker = Join-Path $latestVersion.FullName "x64.complete"
+        $completeMarker | Should -Exist
+    }
+}