chore: update configs submodule — docs/scripts review and cleanup

- README, CONTRIBUTING, QUALITY_GUIDELINES, AGENTS.md all aligned with
  production best practices (accurate counts, no max_pages, unified format)
- validate-config.py: fix two bugs (unified config categories lookup,
  max_pages warning logic)
- Delete old submit-config.md (duplicate of submit-config.yml with
  outdated content)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: yusufkaraaslan