Optional ReadonlydenyOptional ReadonlymodeStrict gate mode for ReadQuery fallbacks.
off: disabled (default).warn: allow but emit structured diagnostics.error: fail on forbidden fallbacks (CI/perf gate).Optional ReadonlyrequireSelectors that must stay on the static lane (keyed by selectorId).
When undefined, the implementation decides the gate coverage (typically all).
Fine-grained kill switch: deny specific fallback reasons (e.g.
unstableSelectorId).