Merge PR #1946: XLSX: keep cell fonts' charset (Arabic 178) and family on save

crates/xlsx/src/styles.rs: family/charset block ported into the dxf.is_none() branch of font_xml (PR #1225 made it take Option<&DxfStated>)
docs/file-format-parity.md: header Change line keeps both sides' clauses

crates/engine/src/cmd/format.rs

@@ -296,7 +296,11 @@ fn underline(s: &mut Session, p: &Json) -> Result<Json> {
 
 fn font_name(s: &mut Session, p: &Json) -> Result<Json> {
     let Some(name) = str_param(p, "name").map(str::to_string) else { return Err(bad("home.fontName", "missing `name`")) };
-    apply_style(s, p, |st| st.font.name = name.clone())
+    apply_style(s, p, |st| {
+        st.font.name = name.clone();
+        st.font.charset = None;
+        st.font.family = None;
+    })
 }
 
 fn font_size(s: &mut Session, p: &Json) -> Result<Json> {

crates/engine/src/tests.rs

@@ -1207,6 +1207,24 @@ fn structured_refs_to_columns_with_edge_spaces() {
     assert_eq!([v(&s, "F1"), v(&s, "F2"), v(&s, "F3")], [n(5.0), n(5.0), n(5.0)]);
 }
 
+#[test]
+fn changing_the_font_name_drops_the_old_fonts_charset_and_family() {
+    let mut s = s();
+    {
+        let wb = std::sync::Arc::make_mut(&mut s.doc_mut().unwrap().wb);
+        let arabic = wb.styles.derive(gridcraft_model::StyleId::DEFAULT, |st| {
+            st.font.name = "Traditional Arabic".into();
+            st.font.charset = Some(178);
+            st.font.family = Some(1);
+        });
+        wb.sheet_mut(0).unwrap().set_style(CellRef::parse("A1").unwrap(), arabic);
+    }
+    s.execute("home.fontName", json!({"range": "A1", "name": "Arial"})).unwrap();
+    let d = s.doc().unwrap();
+    let font = &d.wb.styles.get(d.wb.active().unwrap().style_id(CellRef::parse("A1").unwrap())).font;
+    assert_eq!((font.name.as_str(), font.charset, font.family), ("Arial", None, None));
+}
+
 #[test]
 fn table_rename_keeps_a_defined_name_with_the_same_name() {
     let mut s = s();