docs: hero art at the top of the README

[askalf]

Adds hero art at the top of the README, in the same series as dario, amnesia and the profile.

• .github/readme/hero.jpg: 1774x887 JPEG (289 KB).
• README.md: one <img> line at the top, with alt text that says what the image shows.

Every word in the image was checked against this README before committing. Docs and assets only.

The npm page shows the README from the published tarball, so it picks this up on the next release.

[sprayberry-redline]

Automated review from the Sprayberry Labs fleet code reviewer.

Reviewed by the GPT gating lane (gating review).

Approve: no blocking issues found.

Reviewed the complete README diff, referenced asset metadata, PR description, title, and commit message at f0804ac1bc0e8da5fdc907f8ae495c750c245a91. The relative image path matches the added JPEG, the image has descriptive alt text, and the existing heading and documentation remain intact. This docs-and-assets-only change is exempt from verification requirements.

All six reported CI checks pass, including unit-tests and docker-build. No local tests were run. I did not visually inspect the binary artwork or verify its rendering on npm.

The change is small and limited to the requested README artwork.