docs: add provenance hero to README

[chenmingtang830]

Summary

• Add the generated provenance hero image under assets/articles/.
• Embed it in the README with concise alt text, following the existing centered image convention.
• Keep the two inline article images out because the repository has no existing article-asset section.

Verification

• git diff --check
• Proofpress anchor, snapshot, and verify README.md
• Source and repository image are byte-identical; PNG is 1672×941.

The PR contains only README.md and the new hero image.

[github-actions]

Proofpress

README.md
38efd1df → 81bf5348 ▍ 40 added 14 modified 38 removed
base commit not in ledger — showing last recorded change

• 🟢 new · [![npm version](https://img.shields.io/npm/v/proofpress. · Proofpress
• 🔵 mod · Proofpress
• 🔵 mod · Proofpress
• 🟢 new · Its native ledger travels with Markdown and static HTML · Proofpress
• 🟢 new · > Git made code collaborative. Proofpress makes intellig · Proofpress
• 🟢 new · Think C2PA for knowledge work: a portable, inspectable r · Proofpress
• 🟢 new · ## Why admitted history matters
• 🟢 new · Agent-native work is not a linear document followed from · Why admitted history matters
• 🟢 new · Proofpress operates at that boundary. It does not attemp · Why admitted history matters
• 🟢 new · ## Install
• 🔵 mod · Install
• 🔵 mod · Install
• 🟢 new · ## Try Proofpress in two minutes
• 🟢 new · Start with a real Markdown artifact that already carries · Try Proofpress in two minutes
• 🟢 new · ```sh mkdir proofpress-quickstart && cd proofpress-quick · Try Proofpress in two minutes
• 🟢 new · ![Proofpress inspect, import, and log output](assets/qui · Try Proofpress in two minutes
• 🟢 new · Review the accepted change and check that its recorded c · Try Proofpress in two minutes
• 🟢 new · ```sh npx --no-install proofpress diff strategy.md npx - · Try Proofpress in two minutes
• 🟢 new · ![Proofpress diff and verify output](assets/quickstart/n · Try Proofpress in two minutes
• 🟢 new · Static HTML carries the same native ledger. Download [`s · Try Proofpress in two minutes
• …and 72 more

changelog: Added the hero image as the only README visual change; did not add inline article images.
why: The user authorized publishing the generated provenance hero image in the production README; refresh the portable capsule for the accepted visual block.
🟢 claims verified (1 claims, deterministic check)