Add goal-first review-correctness skill

[shaug]

TL;DR

Adds a repository-owned, goal-first correctness review skill that finds material failures without depending on third-party review skills.

Summary

• Introduces the standalone review-correctness skill and a focused rubric for requirements, security, behavior, compatibility, validation, and material performance risks.
• Grounds findings in the ticket and the reviewed repository's own rules before applying generic guidance.
• Uses the shared review packet and result contracts while preserving strict read-only review behavior.
• Adds raw authorization, missing-test, repository-convention, and standalone ticket-reconstruction evaluations.
• Documents the new skill in the repository catalog and changelog.

Validation

• Repository formatting, linting, skill validation, and test gates pass.
• Fresh forward evaluations found seeded material failures, rejected a clean convention-following change, and reconstructed intent from raw ticket and repository evidence.
• An independent final review found no material ticket-scoped issues at the published head.

Tickets

Fixes #6