chore: validate content consistency and router coverage

[aldegad]

Summary

• add a Node-based validation script for repository content consistency
• add GitHub Actions to run the validation on pushes and pull requests
• align router/meta files so the new validation passes for Robot Security support
• document the validation step in CONTRIBUTING

What the validator checks

• duplicated reference files stay in sync across start/check/fix/guide
• CII and Robot Security reference counts stay consistent with the published tables
• README and router count tables stay aligned with the actual references
• Robot Security routing/metadata coverage does not silently disappear

Why

This repository relies heavily on duplicated markdown references and hand-maintained count tables. That makes it easy for README, skill routers, and copied references to drift apart over time. This PR adds a lightweight guardrail so future guideline updates are easier to trust.

Validation

• ran node scripts/validate-content.mjs

Notes

• this includes the small router/meta consistency fixes required for the new validation to pass on the current main branch
• no converted source documents or PDF assets changed

[nowzero1702]

LGTM

[nowzero1702]

22는 27년도에 단종예정이기에 추후 24이상으로 업데이트 권장