fix: add missing .nojekyll file creation in CI/CD workflow

- Add explicit .nojekyll file creation before each GitHub Pages deployment
- Fix "no such file or directory: build/.*" error in peaceiris/actions-gh-pages
- Ensure Jekyll is properly disabled for all deployments
- Add CNAME creation for smalruby.app deployment

This resolves the CI error where the deployment action was trying to copy
hidden files that didn't exist in the build directory.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: takaokouji

.github/workflows/ci-cd.yml

@@ -106,6 +106,11 @@ jobs:
                 if [[ ${{ contains(github.ref, 'hotfix') }} == 'true' ]]; then
                 sed -e "s|hotfix/REPLACE|${{ github.ref_name }}|" --in-place release.config.js
                 fi
+            - name: Prepare deployment files
+              if: github.ref == 'refs/heads/develop' || github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main'
+              run: |
+                touch build/.nojekyll
+                echo "smalruby.app" > build/CNAME
             - name: Deploy playground to Smalruby.app GitHub Pages
               uses: peaceiris/actions-gh-pages@373f7f263a76c20808c831209c920827a82a2847 # v3
               if: github.ref == 'refs/heads/develop' || github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main'
@@ -122,6 +127,9 @@ jobs:
                 NODE_ENV: production
                 PUBLIC_PATH: /smalruby3-gui/
               run: npm run build
+            - name: Prepare deployment files for smalruby3-gui GitHub Pages
+              if: github.ref == 'refs/heads/develop' || github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main'
+              run: touch build/.nojekyll
             - name: Deploy playground to GitHub Pages
               uses: peaceiris/actions-gh-pages@373f7f263a76c20808c831209c920827a82a2847 # v3
               if: github.ref == 'refs/heads/develop' || github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main'
@@ -147,6 +155,17 @@ jobs:
                 NODE_ENV: production
                 PUBLIC_PATH: /smalruby3-gui/${{ steps.branch.outputs.BRANCH_NAME }}/
               run: npm run build
+            - name: Prepare deployment files for branch GitHub Pages
+              if: |
+                (!(
+                  github.ref == 'refs/heads/develop' ||
+                  github.ref == 'refs/heads/master' ||
+                  github.ref == 'refs/heads/main' ||
+                  startsWith(github.ref, 'refs/heads/hotfix/') ||
+                  startsWith(github.ref, 'refs/heads/dependabot/') ||
+                  startsWith(github.ref, 'refs/heads/renovate/')
+                ))
+              run: touch build/.nojekyll
             - name: Deploy playground to GitHub Pages for branch
               if: |
                 (!(