Customer current MRR state (accountant mirror)

Accountant mirror of the company current-MRR read. An explicit entityId must be one of the customer's concrete entities; absent, the sole concrete entity is selected. Multiple entities require selection (422 ENTITY_SELECTION_REQUIRED); no concrete entity returns 422 ENTITY_SCOPE_UNAVAILABLE. Returns a persisted current recurring run-rate revision, separate from completed-month MRR and movement history. This read performs no provider requests, refresh, publication or financial writes. enabled is presentation permission, not evidence of freshness. An unavailable or withheld current value is null, never fabricated zero. No historical coverage is inferred. Responses use Cache-Control private, no-store.