Fix Pro ESLint config and add vendor ignore to knip

- Explicitly specify eslint.config.mjs for Pro package to avoid
  using root config
- Add react_on_rails/vendor/** to knip ignore list to avoid scanning
  bundled gem dependencies

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

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

Author: justin808

react_on_rails_pro/package-scripts.yml

@@ -39,13 +39,13 @@ scripts:
   eslint:
     default:
       description: Run eslint.
-      script: npx eslint . --report-unused-disable-directives
+      script: npx eslint . --config eslint.config.mjs --report-unused-disable-directives
     fix:
       description: Run eslint and auto-fix.
-      script: npx eslint . --report-unused-disable-directives --fix
+      script: npx eslint . --config eslint.config.mjs --report-unused-disable-directives --fix
     debug:
       description: Run eslint in debug mode.
-      script: DEBUG=eslint:cli-engine npx eslint . --report-unused-disable-directives
+      script: DEBUG=eslint:cli-engine npx eslint . --config eslint.config.mjs --report-unused-disable-directives
 
   format:
     default: