Fix screenshot loop: push to orphan ref instead of PR branch

Committing screenshots to the PR branch caused an infinite loop
(PNG diffs on every run). Now screenshots are pushed to a separate
orphan ref (refs/screenshots/{branch}) which doesn't trigger CI
and doesn't pollute the PR branch.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mmucklo

.github/workflows/ci.yml

@@ -99,9 +99,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-        with:
-          ref: ${{ github.head_ref || github.ref_name }}
-          token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -134,30 +131,33 @@ jobs:
           name: grid-screenshots
           path: Tests/Screenshots/output/*.png
 
-      - name: Commit screenshots to branch
+      - name: Push screenshots to separate ref
         run: |
+          SCREENSHOTS_REF="refs/screenshots/${{ github.head_ref || github.ref_name }}"
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
-          git add -f Tests/Screenshots/output/*.png
-          git diff --staged --quiet && echo "No screenshot changes" && exit 0
-          git commit -m "Update grid screenshots"
-          git push
+          git checkout --orphan screenshots-tmp
+          git rm -rf . > /dev/null 2>&1
+          cp Tests/Screenshots/output/*.png .
+          git add *.png
+          git commit -m "Grid screenshots for ${{ github.head_ref || github.ref_name }}"
+          git push origin HEAD:${SCREENSHOTS_REF} --force
 
       - name: Comment on PR with screenshots
         if: github.event_name == 'pull_request'
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           REPO="${{ github.repository }}"
-          BRANCH="${{ github.head_ref }}"
-          SHA=$(git rev-parse HEAD)
-          BODY="## Grid Screenshots ($(date -u +%Y-%m-%d))
+          SCREENSHOTS_REF="refs/screenshots/${{ github.head_ref }}"
+          REF_SHA=$(git rev-parse HEAD)
+          BODY="## Grid Screenshots
 
           **Table renderer:**
-          ![table](https://raw.githubusercontent.com/${REPO}/${SHA}/Tests/Screenshots/output/table.png)
+          ![table](https://raw.githubusercontent.com/${REPO}/${REF_SHA}/table.png)
 
           **DataTables renderer:**
-          ![datatables](https://raw.githubusercontent.com/${REPO}/${SHA}/Tests/Screenshots/output/datatables.png)
+          ![datatables](https://raw.githubusercontent.com/${REPO}/${REF_SHA}/datatables.png)
 
           _Auto-generated from [CI run](https://github.com/${REPO}/actions/runs/${{ github.run_id }})_"