Macro json 

macro_rules! json {
    (null) => { ... };
    ([ $( $elem:expr ),* $(,)? ]) => { ... };
    ({}) => { ... };
    ({ $( $key:literal : $value:expr ),* $(,)? }) => { ... };
    ($other:expr) => { ... };
}

Re-export shim for the in-house JSON aggregator + json! macro (ADR 0053). Both the crate::json::{Value, Map, to_vec, ...} aggregator module and the crate::json! macro now live in reddb-io-types; this single re-export carries both namespaces so every existing call-site (200+ uses of crate::json::... and crate::json!(...)) compiles unchanged. Replaces the former pub mod json; + local json.rs aggregator.