Rows: a big font isn't counted twice when the sheet's default height already fits it

auto_row_height estimated a line of a bigger font by scaling the sheet's
default row height by size / 11. When the sheet's default already fits
that font, the font counted twice: Excel for Mac saves rows of 16pt text
with defaultRowHeight="21" (28px) and no ht, and opening such a file
fitted every row to 40.7px, 1.45 times Excel's height. Rows mixing Middle
and Bottom aligned cells then looked misaligned.

The estimate now scales an 11pt row's height (DEFAULT_ROW_HEIGHT), so
those rows open at 29px, and rows on a 15pt-default sheet still grow to
their font (#833).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/engine/src/cmd/mod.rs

@@ -484,7 +484,9 @@ pub fn auto_row_height(wb: &mut Workbook, si: usize, row: u32) {
     for (c, cell) in sh.cells.row(row, 0, gridcraft_core::MAX_COLS - 1) {
         let st = wb.styles.get(cell.style);
         let size = st.font.size;
-        let line = (size * 1.8).round().max(default * size / gridcraft_model::DEFAULT_FONT_SIZE);
+        // Scaled from an 11pt row's height, not the sheet's default: a sheet whose default
+        // already fits a bigger font (21pt rows for 16pt text) would otherwise scale it twice.
+        let line = (size * 1.8).round().max(gridcraft_model::DEFAULT_ROW_HEIGHT * size / gridcraft_model::DEFAULT_FONT_SIZE);
         let mut lines = 1.0f32;
         if !cell.value.is_empty() || cell.formula.is_some() {
             let text = crate::display::cell_text(wb, sh, CellRef::new(row, c));