[codex] Add enterprise API change governance

[BobbyZ2026]

/claim #19

Summary

• add a self-contained enterprise-api-change-governance module for enterprise REST API and webhook contract-change review
• evaluate breaking fields, type changes, version windows, critical consumer notice acknowledgement, sandbox evidence, rollback plans, DPA gates for restricted-data webhooks, and webhook envelope/idempotency/signature readiness
• emit admin dashboard metrics, migration actions, signed CloudEvents-style governance events, export manifest evidence, deterministic audit digests, synthetic sample data, docs, tests, SVG report, JSON report, and a short MP4 demo

Distinctness

This slice focuses on pre-release API and webhook contract governance for institutional integrations. It does not duplicate existing #19 submissions for broad dashboards, export packages, compliance evidence packets, audit routing, webhook replay, identity drift, retention/legal hold, grant compliance, data residency, SLA/uptime, secret rotation, lab inventory readiness, or compute/storage quota governance.

References reviewed

• OpenAPI-style machine-readable contract diffs for REST API review
• CloudEvents-style event envelopes for webhook metadata, routing, and replay
• Backward-compatible API evolution practices: versioned releases, deprecation windows, sandbox fixtures, and consumer migration evidence

Demo

• enterprise-api-change-governance/docs/demo.mp4
• enterprise-api-change-governance/docs/demo.svg
• enterprise-api-change-governance/docs/governance-report.json

Validation

• cd enterprise-api-change-governance && npm run check
• cd enterprise-api-change-governance && npm test
• cd enterprise-api-change-governance && npm run demo
• ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,duration -of default=noprint_wrappers=1 enterprise-api-change-governance/docs/demo.mp4
• git diff --check

AI-assisted with OpenAI Codex; I reviewed and locally verified the diff before submitting.