fix(workflow): change trigger to pull_request_target and specify ref for checkout

Author: pauldotyu

.github/workflows/test-e2e-pr.yaml

@@ -3,9 +3,8 @@
 name: test-e2e-pr
 
 on:
-  pull_request:
-    branches:
-      - main
+  pull_request_target:
+    branches: [main]
 
 permissions:
   id-token: write
@@ -20,6 +19,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
 
       - name: Install Terraform
         uses: hashicorp/setup-terraform@b9cd54a3c349d3f38e8881555d616ced269862dd # v3