fix(ci): checkout pr code instead of base branch in claude review

pull_request_target defaults to checking out the base branch HEAD,
not the PR's actual code. Claude was reviewing main branch content
and flagging "missing" changes that the PR itself introduced.

Using ref: head.sha ensures we checkout the PR commit. fetch-depth: 0
provides full history for diff/blame operations. Fork handling step
configures origin correctly for external contributor PRs.

Pattern adopted from vcluster-docs/.github/workflows/claude-review.yml
Closes DEVOPS-501

Author: Piotr1215

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

@@ -28,7 +28,16 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
-          fetch-depth: 1
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: Setup fork as origin for Claude
+        if: ${{ github.event.pull_request.head.repo.fork == true }}
+        run: |
+          git remote rename origin upstream
+          git remote add origin ${{ github.event.pull_request.head.repo.clone_url }}
+          git fetch origin ${{ github.event.pull_request.head.ref }}
+          git checkout -B ${{ github.event.pull_request.head.ref }} origin/${{ github.event.pull_request.head.ref }}
 
       - name: Run Claude Code Review
         id: claude-review