Persist upstream Radar review artifacts

[yvette-carlisle]

Summary

• refresh the deterministic openai/codex upstream Radar queue
• add source-backed bundles, upstream reviews, and impact records for PRs 27490, 27420, 27646, and 27433
• add social candidate handoffs for PR 27420 and PR 27646 only; no social_post/v1 artifacts and no X publishing

Validation

• cargo run -p decodex --bin decodex -- radar bundle validate artifacts/github/bundles/openai-codex-pr-27490.json artifacts/github/bundles/openai-codex-pr-27420.json artifacts/github/bundles/openai-codex-pr-27646.json artifacts/github/bundles/openai-codex-pr-27433.json
• cargo run -p decodex --bin decodex -- radar validate
• cargo make fmt
• cargo make lint-fix
• cargo make test

Notes

• PR 27420 social candidate is publish-worthy practical guidance for nullable plugin app categories.
• PR 27646 social candidate is deferred/watch-note only because orchestrator-only skills are temporarily disabled pending complete hosted skill packages.
• PR 27490 and PR 27433 are kept to review/impact artifacts because their public value is mainly caveated Control Plane tracking.