fix(ci): pull in the upstream base repo branch for PRs

.github/workflows/chromatic.yml

@@ -60,6 +60,13 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.ref }}
           repository: ${{ github.event.pull_request.head.repo.full_name }}
+          fetch-depth: 0
+
+      - name: Fetch base branch for comparison
+        if: github.event_name == 'pull_request'
+        run: |
+          git remote add upstream https://github.com/${{ github.event.pull_request.base.repo.full_name }}.git || true
+          git fetch upstream ${{ github.event.pull_request.base.ref }}
 
       - name: Get changed files
         id: changed-files-yaml
@@ -80,9 +87,9 @@ jobs:
       - name: Publish to Chromatic
         if: ${{ github.actor != 'renovate[bot]' && github.actor != 'renovate' && steps.changed-files-yaml.outputs.src_any_changed == 'true' }}
         uses: chromaui/action@v13
-
-        # Chromatic GitHub Action options
         with:
           workingDir: web
           projectToken: f47410569b62
           onlyChanged: true
+          branch: ${{ github.head_ref || github.ref_name }}
+          sha: ${{ github.event.pull_request.head.sha || github.sha }}