Add event sponsorship revenue readiness guard

[aionathenea-eng]

/claim #20

Summary

Adds a distinct event-sponsorship-revenue-readiness-guard/ module for the Revenue Infrastructure bounty. It evaluates synthetic event sponsorship packets before invoice/revenue release and returns deterministic RELEASE_INVOICE, REVIEW_BEFORE_RELEASE, or HOLD_INVOICE decisions.

Why this slice is distinct

This is not another generic subscription, AI compute, tax, FX, licensing, payment webhook, storage, collections, or grant guard. It targets the event-revenue surface already present in this repo: sponsorship packages, deliverables, sponsor approvals, attendee-lead guarantees, exclusivity conflicts, refund windows, and proof artifacts.

Includes

• Dependency-free Node guard engine
• Synthetic sponsorship packets
• Deterministic tests
• CLI demo
• JSON, Markdown, SVG, and MP4 reviewer artifacts
• Requirement map and safety boundary in README

Validation

• npm run check passed
• npm test passed
• npm run demo passed
• ffprobe on reports/demo.mp4 passed: H.264, 1280x720, 4 seconds, 42 KB
• git diff --check passed

Safety boundary

Synthetic data only. No payment processors, real sponsor/customer data, bank data, credentials, Stripe, PayPal, ERP, CRM, sponsor portals, or external APIs are used.