## Summary
- gate object-tree v2 on exact, schema-backed supersession audit columns
- serialize checked additive DDL and fail closed without disrupting
legacy invoicing
- preserve pre-schema supersession markers when structured columns are
still null
- add a superuser-only, self-scoped canary endpoint with locked
legacy-to-canonical allowlist migration
- verify effective activation, roll back failed readiness, and audit
enable/disable/failure
## Verification
- focused invoicing safety: 16 tests passed (99 assertions)
- full unit suite: 1,237 passed (9,003 assertions), 2 skipped, existing
warnings only
- PHP syntax and `git diff --check` clean
- independent architecture, security, and reviewer gates: GO
## Activation
Deploy with global database/environment enablement off. POST the
self-canary endpoint for one authenticated superuser, require
`configured_enabled=true` and `effective_enabled=true`, then verify the
exact period and tree GET routes. Roll back with the same endpoint using
`enabled=false`.
