Add grant cost-share revenue guard

[wbo68410-lgtm]

/claim #20

Summary

• Adds a distinct grant cost-share revenue guard for issue Revenue Infrastructure #20 Revenue Infrastructure.
• Validates whether subscription, AI compute, and analytics-license charges can be posted to grant-funded or institutional cost-share billing sources before invoicing.
• Checks award dates, allowed charge categories, PI/department approvals, restricted private/commercial usage, cost-share caps, indirect-cost policy, backup billing routes, deterministic audit digests, and finance-ready hold/reroute actions.
• Includes synthetic input data plus deterministic JSON, Markdown, and SVG reviewer artifacts.

Non-overlap

This is a grant and institutional cost-share billing eligibility slice. It is separate from existing billing, metering, payment authorization, renewal notice, receipt privacy, analytics API/seat roster, customer consolidation, collections, prepaid credit, storage overage, tax/FX, and procurement slices.

Verification

• node revenue-infrastructure/grant-cost-share-guard/test.js
• node revenue-infrastructure/grant-cost-share-guard/demo.js
• git diff --check

All data is synthetic; no credentials, private research data, or external services are used.

Closes #20