[codex] Add ChatGPT Desktop to implementation status

[nmccormack-oai]

Summary

• Add ChatGPT Desktop to the WebMCP implementation-status list.
• Update the introduction to cover browser and client implementations.
• Check in the OpenAI Blossom SVG so the status page does not depend on a browser-only logo repository.

Why

• ChatGPT Desktop supports WebMCP but is not represented on the implementation-status page.
• The existing logo source only hosts browser logos, so keeping the OpenAI asset in this repository avoids a cross-repository dependency and a separate upstream contribution.

Validation

• Ran git diff --check.
• Parsed assets/openai.svg with xmllint --noout.
• Confirmed the SVG path comes from the official OpenAI logo package; only its intrinsic size and viewport were adjusted.
• Confirmed the fork branch and local branch point to the same commit.

[w3cbot]

victorhuangwq marked as non substantive for IPR from ash-nazg.

[victorhuangwq]

cc:// @beaufortfrancois and @domfarolino

I marked it as non-substantive as per https://www.w3.org/policies/process/#substantive-change since it does not touch any of the spec text.