Function feature_default_params 

pub fn feature_default_params(feature_type: &str) -> Value

A feature type’s DEFAULT inputParams, built from its schema: one entry per inputParamsSchema param seeded with that param’s default_value (missing → null). The caller assigns the unique id afterwards (the schema’s id default is null). Additive, engine-owned, and reusable by any “add feature” path so a new feature’s params always track the kernel schema. Unknown types yield an empty object.