Add communication guidelines and PR review skill

[ivan-digital]

Summary

• Add communication guidance to lead with conceptual status, risk, tests, and recommendation.
• Add a /review-pr project skill for architecture fit, adversarial review, security review, docs impact, regression risk, test coverage, and merge readiness.
• Require review summaries to report E2E tests run, or explain why E2E does not apply.
• Add repo-local .codex/skills relative symlinks so agents that scan that path can use the same project skills from .claude/skills.
• Add the new review command to the project skills table.

Validation

• git diff --check
• Parsed the new skill frontmatter locally
• Verified .codex/skills symlinks resolve locally

Runtime tests were not run because this is guidance-only.