ci: Add new power PR check workflow

.github/workflows/new-power-check.yml

@@ -0,0 +1,76 @@
+name: New Power PR Check
+
+on:
+  pull_request:
+    types: [opened]
+
+permissions:
+  pull-requests: write
+  contents: read
+
+jobs:
+  check-new-power:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Detect new power folders
+        id: detect
+        run: |
+          SKIP_DIRS=".git .github .kiro checkout"
+
+          # Get folders that exist on the base branch
+          BASE_FOLDERS=$(git ls-tree --name-only -d "origin/${{ github.event.pull_request.base.ref }}" 2>/dev/null || true)
+
+          # Get top-level folders touched in this PR
+          PR_FOLDERS=$(git diff --name-only "origin/${{ github.event.pull_request.base.ref }}...HEAD" \
+            | cut -d'/' -f1 \
+            | sort -u)
+
+          NEW_FOLDERS=""
+          for folder in $PR_FOLDERS; do
+            # Skip files (no directory in diff)
+            [ -d "$folder" ] || continue
+
+            # Skip meta directories
+            skip=false
+            for s in $SKIP_DIRS; do
+              [ "$folder" = "$s" ] && skip=true && break
+            done
+            $skip && continue
+
+            # Check if folder existed on base branch
+            if ! echo "$BASE_FOLDERS" | grep -qx "$folder"; then
+              NEW_FOLDERS="$NEW_FOLDERS $folder"
+            fi
+          done
+
+          NEW_FOLDERS=$(echo "$NEW_FOLDERS" | xargs)
+          echo "new_folders=$NEW_FOLDERS" >> "$GITHUB_OUTPUT"
+          if [ -n "$NEW_FOLDERS" ]; then
+            echo "has_new=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "has_new=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Comment on PR
+        if: steps.detect.outputs.has_new == 'true'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const user = context.payload.pull_request.user.login;
+            const body = [
+              `Hi @${user}, thank you for your contribution!`,
+              '',
+              'Please note that if you haven\'t already, you would also need to submit your power officially at [kiro.dev/powers/submit](https://kiro.dev/powers/submit) so it can be reviewed for listing in the Kiro powers registry.'
+            ].join('\n');
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body
+            });