Publish Codex alpha.6 release checkpoint

[yvette-carlisle]

Summary

• refresh the openai/codex release_delta/v1 artifact to rust-v0.138.0-alpha.6
• add a durable skip candidate for the superseded alpha.5 checkpoint
• add a publishable alpha.5 -> alpha.6 prerelease thread candidate with PR-title gap list and source-review caveats

Evidence

• official GitHub release metadata: rust-v0.138.0-alpha.5 published 2026-06-05T23:27:47Z; rust-v0.138.0-alpha.6 published 2026-06-06T03:23:40Z
• adjacent compare metadata: rust-v0.138.0-alpha.5...rust-v0.138.0-alpha.6 has 11 ahead commits and status diverged
• official Codex changelog RSS had no newer Codex app/mobile/changelog entry than the already handled 2026-06-04 app update

Validation

• jq empty artifacts/github/social-candidates/openai-codex-rust-v0-138-0-alpha-5-superseded-skip.json artifacts/github/social-candidates/openai-codex-rust-v0-138-0-alpha-6-prerelease-delta.json site/src/content/release-deltas/openai-codex-latest.json
• jq candidate_text length check, all entries <= 280 chars
• git diff --check
• cargo run -p decodex --bin decodex -- radar validate site/src/content/release-deltas/openai-codex-latest.json artifacts/github/social-candidates/openai-codex-rust-v0-138-0-alpha-5-superseded-skip.json artifacts/github/social-candidates/openai-codex-rust-v0-138-0-alpha-6-prerelease-delta.json
• cargo make check-site-content

[yvette-carlisle]

Closing as duplicate. The automation memory points to PR #226 as the existing durable alpha.5 skip + alpha.6 publish handoff; PR #226 is open and green, so leaving this duplicate would create competing social_candidate/v1 artifacts.