Add Affinity agent-native WebMCP telehealth demo

[Dawsson]

Summary

• expose three public synthetic patient tools and two authenticated Affinity Test draft tools through document.modelContext.registerTool
• share one prescribing workflow seam across synthetic demo and hosted Affinity Test adapters
• require an explicit clinician confirmation before unsigned Test order creation
• add MIT license, safety/design contracts, tests, evaluator cases, and submission docs

Verification

• bun run check (22 tests)
• bun run build
• native Chrome WebMCP discovery and execution smoke
• desktop/mobile Impeccable review: ship

Safety

Affinity Test and synthetic data only. The tools cannot confirm, create, sign, submit, or transmit a prescription. This PR must not be merged before challenge review.

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