fix(properties): preserve literal text

Separate numeric fields from names and content so only numeric property values are evaluated as expressions.

Refs #809

src/entities/mtext.rs

@@ -260,7 +260,7 @@ fn properties(t: &MText, text_style_names: &[String]) -> Vec<PropSection> {
                 Property {
                     label: t!("Contents").into_owned(),
                     field: "content",
-                    value: PropValue::EditText(t.value.clone()),
+                    value: PropValue::PlainText(t.value.clone()),
                 },
                 Property {
                     label: t!("Style").into_owned(),