Function json_value_to_toml_value 

pub fn json_value_to_toml_value(jv: &JsonValue) -> Value

Convert a JsonValue into a toml::Value.

Used by N7 consumer C11 (toml.stringify). Pair with heap_to_json_value to round-trip a HeapValue tree to a TOML string via toml::to_string(&v)?. Replaces the legacy nanboxed_to_toml_value walker (stdlib/toml_module.rs:67-107) entirely; that walker used deleted ValueWord accessors and is removed by C11.

TOML constraint: TOML has no native null. JsonValue::Null maps to toml::Value::String("null") — the same lossy sentinel used by the legacy nanboxed_to_toml_value walker (toml_module.rs:68-70), preserved here for round-trip behavior continuity. Reconsidering this sentinel is a future architectural-choice sub-decision (the alternative — refusing serialization with Err — would be a behavioral regression vs the legacy walker; held as future N7 sub-disposition).

TOML constraint: TOML’s top-level must be a Table. This helper returns a toml::Value of any shape; the consumer (toml.stringify body in C11) is responsible for verifying root-level Table when passing to toml::to_string. Surfacing root-level non-Table as Err is C11’s responsibility, not this helper’s.

JsonValue::Bytes maps to Array of u8-as-Integer (TOML has no native byte type); reserved for future msgpack-binary roundtrip via 3.C.