Persist Codex alpha.2/alpha.3 checkpoint defers

[yvette-carlisle]

Summary

• Refresh release_delta/v1 to stable rust-v0.138.0 -> latest prerelease rust-v0.139.0-alpha.3.
• Add terminal social_candidate/v1 defer records for rust-v0.139.0-alpha.2 and rust-v0.139.0-alpha.3.
• Record adjacent prerelease lineage, sparse release-body caveats, quote-chain caveats, and exact source-review gap lists.

Decision

• selected mode: watch_note
• decision.worthiness: defer
• reason: needs_upstream_analysis
• do not hand these records to decodex-x-publisher until the listed PRs receive upstream source review.

Validation

• target/debug/decodex radar validate artifacts/github/social-candidates site/src/content/release-deltas passed: OK (29 Radar artifact JSON files validated).
• jq schema/text-length check passed for the alpha.3 candidate (candidate_text length 274).
• git diff --check passed.
• cargo make fmt passed.
• cargo make lint-fix passed; vstyle checked 103 files and applied 0 fixes.
• cargo make test passed: 971 tests run, 971 passed, 1 skipped.