pub fn eval_main(instance: &Value, ctx: &Ctx) -> Result<Option<Value>, Raised>Expand description
Evaluates the __main body of a module instance in its own environment.
Returns Ok(None) if no body is declared (e.g., a library).
This implements “runnable” module semantics: crate::load_module instantiates
modules without evaluating their bodies, ensuring __main is only executed
when explicitly targeted by a runner.
The body executes in the instance’s Module terminal.
As it is not a member, it has no reserved ID. Non-module instances raise
.not_a_module. Result interpretation is handled by the runner; see
docs/done/2026-08-14_elly-run.md.