feat: Scientific Bounty & Research Marketplace Engine specification (Fixes #18)

[techsp13]

Fixes #18

Summary of Changes

Implements the comprehensive architectural specification for the Scientific Bounty & Research Marketplace Engine in scientific-bounty-system/README.md.

Core Capabilities Documented:

• Challenge Creation & Tiered Escrow: Winner-takes-all, milestone-based, and proportional leaderboard reward distributions.
• End-to-End Bounty Lifecycle: Detailed Mermaid sequence diagram tracing challenge sponsorship through automated benchmark evaluation and escrow release.
• Automated Sandbox Verification: Ephemeral containerized evaluation pipelines against hidden validation datasets.
• Full API Specification: Complete REST endpoints for challenge publishing, artifact submission, leaderboard queries, and automated escrow payout authorization.
• Security & IP Safeguards: Zero-knowledge cryptographic commitment hashing protecting solver intellectual property.