docs: link the README's logo by absolute URL so it renders on PyPI

[earakely-scale]

pyproject.toml publishes README.md as the PyPI description (readme = "README.md"). PyPI can't resolve paths relative to the repository, so the logo from #6 (assets/brand/lockup-light.png) would render as a broken image on the package page. Both lockups now link to https://raw.githubusercontent.com/scaleapi/agentenv-framework/main/assets/brand/…, which serves them now that the repo is public.

On GitHub: nothing changes. The <picture> still shows the light or dark lockup to match the reader's theme.

On PyPI: checked with PyPI's own renderer, readme_renderer[md] 46.0. It keeps <picture> and <img> but strips the dark-mode <source>, so PyPI always shows the light lockup. Before this change its src was the relative path; now it's the absolute URL.

Checked:

• uv build, then twine check on both the wheel and the sdist: PASSED.
• Both raw URLs return 200 image/png without authentication.

🤖 Generated with Claude Code

Confidence Score: 5/5

The PR appears safe to merge.

Summary

The README now loads its light and dark logos from public image URLs, so they render in package descriptions too.

• GitHub keeps its theme-based logo choice.
• PyPI can load the light logo after removing the dark-mode source.

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