FLEX-WP-0014. Package tenant-engine.write-api.mutate v1 now carries
nine actions: tenant.guardrail.read and tenant.guardrail.set on
resource type guardrail, verbatim from tenant-engine's mapping.
The read/write split is used now: flex-auth may read ceilings and is
denied action_not_granted on set; tenant-engine may do both. 17/17
Rego tests and 23/23 fixtures pass. Live e2e against a real
tenant-engine FlexAuthWriteAuthorizer matches.
In source only; production still serves the seven-action 9320df39 pin.
