Slice: Add continuum.contract.index.v1 profile fixture

[flyingrobots]

Slice

Add the contract index profile proof from the Continuum Compendium.

Done when:

• participants can list authored, consumed, and emitted contract families;
• schema digests, generated artifact refs, compatibility claims, conformance witness refs, and open cuts are machine-readable;
• generated artifacts are evidence/integration surfaces, not semantic owners;
• continuum.contract.index.v1 composes with participant hello and observation profile fixtures.

Part of #59.

[coderabbitai]

🔗 Related PRs

#19 - Add cross-repo contract family registry [merged]

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