build(ci): improve 'screenshot-diff' directory structure

* remove the nested folder tree (build/outputs/roborazzi)
* name the directory: screenshot-diff.zip contains
`screenshot-diff-pr-123` so conflicts don't occur and cleanup is easier

Assisted-by: Claude Opus 4.7 - all

Issue 20942

Author: david-allison

.github/workflows/screenshot_comment.yml

@@ -65,8 +65,8 @@ jobs:
         name: Check if there are valid files
         shell: bash
         run: |
-          # Find roborazzi diff PNGs in the downloaded artifact.
-          mapfile -t files_to_add < <(find . -path '*/roborazzi/*' -name "*_compare.png" -type f)
+          # Find roborazzi diff PNGs in the downloaded artifact (in <TestClass>/diffs/).
+          mapfile -t files_to_add < <(find . -path '*/diffs/*' -name "*_compare.png" -type f)
           if [ ${#files_to_add[@]} -gt 0 ]; then
             exist_valid_files="true"
           else
@@ -83,17 +83,17 @@ jobs:
           BASE_REF: ${{ github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.pull_requests[0].base.ref || github.event.repository.default_branch }}
         shell: bash
         run: |
-          # Find roborazzi diff PNGs to mention in the comment.
-          mapfile -t files < <(find . -path '*/roborazzi/*' -name "*_compare.png" -type f | sort)
+          # Find roborazzi diff PNGs to mention in the comment (in <TestClass>/diffs/).
+          mapfile -t files < <(find . -path '*/diffs/*' -name "*_compare.png" -type f | sort)
           total=${#files[@]}
           # Cap the full list so we remain within GitHub's comment limit
           max_details=100
 
-          # Group by test class — the directory immediately under roborazzi/.
+          # Group by test class — the directory containing diffs/.
           declare -A class_counts class_files
           for file in "${files[@]}"; do
-            rest="${file#*/roborazzi/}"
-            class="${rest%%/*}"
+            class_dir="${file%/diffs/*}"
+            class="${class_dir##*/}"
             class_counts[$class]=$(( ${class_counts[$class]:-0} + 1 ))
             class_files[$class]+="$(basename "$file")"$'\n'
           done

.github/workflows/screenshot_compare.yml

@@ -67,13 +67,24 @@ jobs:
         run: |
           ./gradlew compareRoborazziPlayDebug -Pscreenshot --stacktrace
 
+      - name: Stage screenshot diffs
+        if: ${{ always() }}
+        env:
+          # Folder name inside the artifact (e.g. "screenshot-diff-pr-12345" on PRs, "screenshot-diff-main" on push)
+          SUBDIR: ${{ github.event_name == 'pull_request' && format('screenshot-diff-pr-{0}', github.event.number) || format('screenshot-diff-{0}', github.ref_name) }}
+        run: |
+          # Trim 'AnkiDroid/build/outputs/roborazzi' from the artifact and namespace by PR/branch
+          mkdir -p screenshot-diff
+          if [ -d AnkiDroid/build/outputs/roborazzi ]; then
+            mv AnkiDroid/build/outputs/roborazzi "screenshot-diff/$SUBDIR"
+          fi
+
       - name: Upload screenshot diffs
         uses: actions/upload-artifact@v4
         if: ${{ always() }}
         with:
           name: screenshot-diff  # referenced by screenshot_comment.yml
-          path: |
-            **/build/outputs/roborazzi
+          path: screenshot-diff
           retention-days: 30
 
       - name: Upload screenshot diff reports