Add grandfathered pricing migration guard

[snkk2x-collab]

/claim #20

Summary

• add a self-contained grandfathered-pricing-migration-guard package for Revenue Infrastructure
• evaluate whether legacy-price accounts can be migrated to a new price book before invoice release
• cover active price locks, notice windows, material-increase consent, annual/volume discount compatibility, add-on parity, seat/compute entitlement regressions, currency approval, and reviewer evidence

Distinct scope

This is not a generic subscription ledger, usage meter, coupon/consortium pricing guard, quota rollover guard, committed-usage true-up, grant compute budget, FX settlement, invoice delivery, tax/VAT, dunning, or analytics-seat licensing slice. It focuses only on legacy price-book migration release decisions.

Reviewer artifacts

• grandfathered-pricing-migration-guard/artifacts/pricing-migration-results.json
• grandfathered-pricing-migration-guard/artifacts/pricing-migration-report.md
• grandfathered-pricing-migration-guard/artifacts/pricing-migration-summary.svg
• grandfathered-pricing-migration-guard/artifacts/pricing-migration-demo.mp4
• grandfathered-pricing-migration-guard/artifacts/demo-transcript.md

Validation

• node scripts/demo.js
• node --test
• node --check src/index.js
• node --check scripts/demo.js
• node --check test/pricingMigrationGuard.test.js
• git diff --check

Boundaries

Synthetic account packets only. No payment processor calls, no customer systems, no bank rails, no credentials, no external APIs, and no private billing records.

AI-assisted with OpenAI Codex; I reviewed and verified the isolated module before submission.