Function is_lever 

pub fn is_lever(name: &str) -> bool

2026-09-26: Whether name is a serve lever: any METRALE_* name that is not a harness variable.

The harness variables are the table’s Class::Harness entries (metrale_config::levers): they place, log or build for the harness. Every other name under the prefix counts, including one the table does not declare, so the harness names it in a refusal; met itself refuses to start with an undeclared one set (levers::check in main.rs).