Function emit 

pub fn emit(id: SchemaId) -> Result<(), AppError>

Emit the compact JSON Schema for id to stdout and flush.

Stdout contains only the schema document (one compact JSON line) so agents can pipe the output into a validator without filtering tracing noise.

Errors

Returns AppError::Validation if the embedded schema is not valid JSON (should never happen for the checked-in files) or an I/O error from stdout.