Publish the skill's own icon, banner and card with a persistent key chip #132

Problem

The repository still ships an older hand-composed banner and card (docs/images/banner.png, docs/images/card.svg) and no skill icon of its own. After the alpha-fit renderer fix (#130, merged) the skill's own outputs can be produced by the real CLI from fresh public metadata, but nothing committed reflects that, and the final key chip ("Claude + Codex") is only reproducible by a one-off banner invocation: .github/showcase.yml carries only the subtitle, so a normal Action regeneration would drop it.

Expected

• A normalized icon for the skill produced by the merged content icon normalize CLI from the preserved raw Codex image, with the exact final bytes and hash recorded in the PROMPTS provenance block (no hand-edited pixels).
• The repository's own banner, card and social/contact-sheet outputs regenerated through the final showcase.py from freshly fetched public metadata.
• The key chip persisted through the supported configuration (.github/showcase.yml chips.key, already honoured by chips.key_chips) so normal regeneration preserves it; regenerating from the committed configuration must reproduce the committed outputs byte for byte.

Acceptance

• Committed assets are byte-identical to the visually accepted private render of the merged CLI (hash comparison), no generated asset is hand-edited, raw source preserved.
• A test or documented check proves the key chip comes from the configuration, not a flag.
• Exact-head VM, regeneration hash replay, root visual review, two Opus and Sol, hosted CI.

Prior work

Searched open and closed issues and PRs for key chip, showcase.yml key, regenerate assets, icon provenance and banner card social own: only #98 (banner requires a description; card chip flags) is adjacent and not duplicated, and merged #130, #126, #129 are reused.