Engine: only hidden names are read as macro storage

A visible workbook-scope name such as `_gc_macro_0_0` matched the storage key and was read as a
macro and removed when the workbook opened. Macro storage is written hidden, so only hidden names
are read back; a person's own name of that shape stays a name.

crates/engine/src/macros/mod.rs

@@ -177,7 +177,9 @@ pub fn load(wb: &mut Workbook) -> Vec<String> {
 
 /// The item key (`macro_<n>`, lower-cased) of a hidden macro name, and `n` when it is a number.
 fn macro_item(n: &DefinedName) -> Option<(String, Option<u64>)> {
-    let key = stash::item_key(&n.name).filter(|k| n.scope.is_none() && k.starts_with(MACRO_KEY))?;
+    // Only a hidden workbook-scope name is macro storage: a person's own visible name that
+    // happens to look like one stays a name.
+    let key = stash::item_key(&n.name).filter(|k| n.hidden && n.scope.is_none() && k.starts_with(MACRO_KEY))?;
     let i = key.strip_prefix(MACRO_KEY).and_then(|i| i.parse().ok());
     Some((key, i))
 }

crates/engine/src/macros/tests.rs

@@ -127,6 +127,19 @@ fn hidden(name: &str, text: &str) -> DefinedName {
     DefinedName { name: name.into(), scope: None, formula: format!("\"{}\"", text.replace('"', "\"\"")), comment: String::new(), hidden: true }
 }
 
+#[test]
+fn a_visible_name_that_looks_like_macro_storage_is_left_alone() {
+    // Macro storage is hidden workbook-scope names; a visible `_gc_macro_0_0` someone defined
+    // is neither read as a macro nor removed when the workbook opens.
+    let mut wb = Workbook::new();
+    let name = DefinedName { hidden: false, ..hidden("_gc_macro_0_0", "x") };
+    wb.names.push(name.clone());
+    let warnings = load(&mut wb);
+    assert!(warnings.is_empty(), "{warnings:?}");
+    assert!(wb.macros.is_empty());
+    assert_eq!(wb.names, vec![name]);
+}
+
 #[test]
 fn scripts_and_vba_stay_as_they_are() {
     // Automate scripts keep their own storage, and a VBA project is carried through unchanged.