Persist upstream Radar review artifacts

[yvette-carlisle]

Summary

• refreshed the openai/codex upstream review queue at 2026-06-16T12:38:20Z with search_limit 40
• added github_change_bundle/v1, upstream_review/v1, upstream_impact/v1, and social_candidate/v1 artifacts for openai/codex PR #27902
• no social_post/v1 records were written and nothing was published to X

Validation

• cargo run -p decodex --bin decodex -- radar bundle validate artifacts/github/bundles/openai-codex-pr-27902.json
• cargo run -p decodex --bin decodex -- radar validate artifacts/github/review-queue artifacts/github/reviews artifacts/github/impact artifacts/github/social-candidates artifacts/github/bundles
• git diff --check
• cargo make check-site-content

Notes

• selected PR #27902 from the deterministic queue because it had no matching source-backed upstream_review/v1 artifact and touches auth-dependent plugin app/MCP routing
• downstream Publisher automation should consume the social_candidate/v1 artifact; this PR does not publish