Extrude: a symmetric distance is the total thickness (#1260)

A symmetric solid extrude of 10 mm is now 10 mm thick, 5 mm each side of the sketch plane, and switching from One Side to Symmetric keeps the thickness entered. Under format 21 the extent records its convention; designs saved without it keep the per-side reading, so their geometry and parameters don't change. Fixes #1236.

Co-authored-by: Karl-VonRichter <Karl-VonRichter@users.noreply.github.com>

apps/solidcraft-cli/src/recipe.rs

@@ -92,7 +92,7 @@ fn extent(f: &Value, p: &mut Value) {
         "symmetric" => {
             let full = e.get("is_full_length").and_then(Value::as_bool).unwrap_or(false);
             p["direction"] = json!("symmetric");
-            p["distance"] = if full { json!(format!("({}) / 2", expr_text(&dist))) } else { dist };
+            p["distance"] = if full { dist } else { json!(format!("({}) * 2", expr_text(&dist))) };
         }
         "two_sides" => {
             p["distance"] = e.get("side1").cloned().unwrap_or(Value::Null);