Fix jest-junit reporter error in CI (#ISSUE)

The CI was failing with two issues:
1. jest-junit module not found in node-renderer package
2. ESLint couldn't resolve react-on-rails imports in Pro package

Changes:
- Add jest-junit ^16.0.0 to node-renderer devDependencies
- Add jest-junit to root package devDependencies for consistency
- Add build step to pro-lint workflow before linting
- Add junit.xml to .gitignore

The build step is required because Pro package imports from react-on-rails,
and ESLint needs the built lib/ files to resolve module paths. Without
building first, ESLint import resolution fails with "Cannot find module"
errors.

Fixes:
- Error: Could not resolve a module for a custom reporter (jest-junit)
- ESLint import/no-duplicates, import/no-self-import, import/no-cycle errors

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

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

Author: justin808

.github/workflows/pro-lint.yml

@@ -161,6 +161,10 @@ jobs:
       - name: Generate file-system based entrypoints
         run: cd spec/dummy && bundle exec rake react_on_rails:generate_packs
 
+      - name: Build react-on-rails package (required for Pro eslint import resolution)
+        working-directory: .
+        run: yarn build
+
       - name: Lint Ruby
         run: bundle exec rubocop --ignore-parent-exclusion