Publish Codex alpha.6 release checkpoint

[yvette-carlisle]

Summary

• Records the alpha.6 prerelease candidate and terminal @decodexspace X thread.
• Consumes the alpha.6 social publish reservation after live Chrome publication.
• Normalizes the Codex app 26.602 publication record to the canonical media-attached post and keeps the later text-only duplicate only as audit evidence.

Publication

• https://x.com/decodexspace/status/2063279620129247678
• https://x.com/decodexspace/status/2063279622410870898
• https://x.com/decodexspace/status/2063279624575205432
• https://x.com/decodexspace/status/2063279626819141750
• https://x.com/decodexspace/status/2063279628933042178
• Media readback: https://x.com/decodexspace/status/2063279620129247678/photo/1

Validation

• jq empty on the new alpha.6 post and consumed reservation
• git diff --check
• cargo run -p decodex --bin decodex -- radar validate artifacts/github/social-candidates artifacts/social/x
• cargo make check-site-content

Notes

• Record Codex app 26.602 X publication #225 is superseded by this branch because main already had the same app 26.602 post path, creating an add/add conflict. This PR carries the canonicalized app record plus the completed alpha.6 publication.