- Add upsert_deny_policy / remove_deny_policy to IAMService
- Auto-update Deny policy when adding/removing projects
- Auto-create Deny policy on sub-account creation
- Deny policy lists all non-authorized projects explicitly
- Verified: cross-project ListAssetGroups and ListApiKeys are blocked
- Updated research report with cross-project API findings (2026-03-28)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>