ci: use pull_request_target for claude review on fork PRs (#10)

Author: ascorbic

.github/workflows/claude-code-review.yml

@@ -1,7 +1,7 @@
 name: Claude Code Review
 
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, synchronize]
     # Optional: Only run on specific file changes
     # paths:
@@ -29,6 +29,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
+          ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 1
 
       - name: Run Claude Code Review