Add verified one-arc composer study

[devinnicholson]

What changed

• adds the complete 42-edit authorial demonstration to the fixed-value atlas
• binds the panel to the frozen protocol and independent verification artifacts
• lets readers inspect the starting graph, each one-arc toggle, and the selected exact result
• removes the redundant aesthetic-scope disclaimer from the public evidence narrative
• extends rendering, evidence-contract, and accessibility tests

Why

The paper now reports a performed creative-practice encounter rather than a hypothetical composer workflow. The public atlas should expose the same complete, independently verified result.

Validation

• npm run lint under Node 22.17.0
• npm test under Node 22.17.0 (5/5 tests passed)

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