[codex] Move detailed install commands to README end

[Zer0pa-Architect-Prime]

Summary

• keep a minimal package/boundary cue at the top of the README
• move the full install, smoke, source, and developer commands to a detailed section at the end
• add a stable top jump link to the detailed section

Validation

• README-only change
• original product front-door body is preserved byte-for-byte
• original install/developer content is preserved byte-for-byte in the new detailed section