fix: rename assert asset directory and update references

[zilongzheng]

Summary

• Rename the top-level assert/ directory to assets/.
• Update README links, chart defaults, the Pages build script, and workflow filters to use the corrected path.
• Add the case-study PNG alongside its SVG source.

Testing

• git diff --check
• Confirmed no residual assert/ references remain.
• Built the GitHub Pages site successfully in a temporary directory.
• Generated benchmark summary and overview SVGs using temporary outputs.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T04:30:58.056826Z	aba014d	PR opened

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