Add diff review mode with before/after comparisons

.github/workflows/example-basic.yml

@@ -23,3 +23,4 @@ jobs:
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           renderer: metadata  # No screenshots, just frame info
+          comment-id: basic

.github/workflows/example-diff.yml

@@ -0,0 +1,32 @@
+# Example: Diff Design Review (Before/After Comparison)
+# Shows only changed frames with side-by-side before/after screenshots.
+# Uses the pencil-screenshot-service diff endpoint.
+
+name: Design Review (Diff)
+on:
+  pull_request:
+    paths:
+      - '**/*.pen'
+
+jobs:
+  design-review:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+      id-token: write    # Required for OIDC authentication
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run Design Review (Diff Mode)
+        uses: remotestate/pencil-actions@v1
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          renderer: service
+          service-url: https://pencil.remotestate.com
+          review-mode: diff
+          comment-id: diff
+          image-format: webp
+          image-scale: 2

.github/workflows/example-visual.yml

@@ -26,6 +26,8 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           renderer: service
           service-url: https://pencil.remotestate.com
+          review-mode: full
+          comment-id: visual
           max-frames-per-file: 10
           image-format: webp
           image-scale: 3

.github/workflows/test-action.yml

@@ -24,5 +24,6 @@ jobs:
           renderer: service
           service-url: https://pencil.remotestate.com
           service-api-key: ${{ secrets.SCREENSHOT_API_KEY }}
+          comment-id: test
           image-format: webp
           image-scale: 3

action.yml

@@ -16,6 +16,11 @@ inputs:
     required: false
     default: 'service'
 
+  review-mode:
+    description: 'Review mode: "full" (render all frames) or "diff" (show only changes with before/after comparison)'
+    required: false
+    default: 'diff'
+
   service-url:
     description: 'Screenshot rendering API URL'
     required: false
@@ -35,6 +40,11 @@ inputs:
     required: false
     default: 'update'
 
+  comment-id:
+    description: 'Unique identifier to namespace PR comments. Allows multiple workflows to post separate comments on the same PR without overwriting each other.'
+    required: false
+    default: ''
+
   upload-artifacts:
     description: 'Whether to upload screenshots as workflow artifacts'
     required: false