github-workflow: Use pull_request_target for e2e pending status

Switch from pull_request to pull_request_target so the GITHUB_TOKEN
has write access to commit statuses even for fork PRs. The job only
posts a status and never checks out PR code, so this is safe.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ganto

.github/workflows/e2e.yaml

@@ -3,7 +3,7 @@ name: E2E Tests
 
 on:
   workflow_dispatch:
-  pull_request:
+  pull_request_target:
 
 permissions:
   contents: read
@@ -12,7 +12,7 @@ permissions:
 jobs:
 
   set-pending:
-    if: github.event_name == 'pull_request'
+    if: github.event_name == 'pull_request_target'
     runs-on: ubuntu-latest
     name: Set pending e2e status
     steps: