fix: a size worked out from a bare diameter keeps its unit when the design's units change (#716) (#779)

A size typed as a bare diameter now keeps the design's length unit, so it no longer changes when the design's units change. Fixes #716.

crates/doc/src/params.rs

@@ -466,7 +466,7 @@ impl Document {
     /// in (feature inputs are stored in mm otherwise). Anything else is returned unchanged.
     pub fn with_design_unit(&self, e: &str, kind: Kind) -> String {
         let u = self.units.trim();
-        let bare = expr::is_literal(e) && e.trim().trim_start_matches(['-', '+']).trim().parse::<f64>().is_ok();
+        let bare = expr::is_bare_number(e);
         if kind == Kind::Length && bare && !u.is_empty() && u != "mm" && expr::unit_info(u).is_some_and(|(k, _)| k == Kind::Length) {
             format!("{} {u}", e.trim())
         } else {