Fuzzer: switching Normal, Page Layout or Page Break Preview isn't an undo difference

The view commands are not undo steps and don't mark the workbook changed (as in
Excel), so undoing everything leaves a sheet's view mode as it is. The undo
check now resets the view mode with the other view state before comparing.
Seed 177 (`view.pageBreakPreview` on the sales sample) failed the [undo]
invariant without this.

crates/engine/tests/it/command_sequence_fuzz.rs

@@ -34,7 +34,7 @@ use std::sync::Arc;
 
 use gridcraft_core::{CellRef, MAX_COLS, MAX_ROWS, RangeRef, Value, col_to_letters};
 use gridcraft_engine::calc::Calc;
-use gridcraft_engine::model::{CalcMode, Formula, Sheet, Workbook};
+use gridcraft_engine::model::{CalcMode, Formula, Sheet, SheetViewMode, Workbook};
 use gridcraft_engine::{EngineError, Session, command_specs, find_command, io};
 use serde_json::{Value as Json, json};
 
@@ -486,8 +486,9 @@ fn watch_list(wb: &Workbook) -> Option<&str> {
     wb.names.iter().find(|n| n.name == WATCH_NAME).map(|n| n.formula.as_str())
 }
 
-/// The workbook with view state (active sheet, scroll, active cell) and the Watch Window list
-/// reset: undo restores view state as it was, but switching sheets isn't an undoable edit.
+/// The workbook with view state (active sheet, scroll, active cell, Normal / Page Layout / Page
+/// Break Preview) and the Watch Window list reset: undo restores view state as it was, but
+/// switching sheets or views isn't an undoable edit.
 fn canonical(wb: &Workbook) -> Workbook {
     let mut wb = wb.clone();
     wb.set_active_sheet(0);
@@ -496,6 +497,7 @@ fn canonical(wb: &Workbook) -> Workbook {
         let sh = Arc::make_mut(sh);
         sh.view_active = CellRef::default();
         sh.view_top_left = CellRef::default();
+        sh.view = SheetViewMode::Normal;
     }
     wb
 }
@@ -1089,3 +1091,13 @@ fn params_docs_parse_into_keys() {
         assert!(find_command(id).is_some(), "CURATED names unknown command `{id}`");
     }
 }
+
+/// Seed 177: switching a sheet to Page Break Preview isn't an undo step (as in Excel), so undoing
+/// everything leaves the view mode alone and the undo check must not count it as an edit.
+#[test]
+fn view_mode_switch_is_not_an_undo_difference() {
+    for id in ["view.pageBreakPreview", "view.pageLayout"] {
+        let failure = replay("sales", &[(id.to_string(), json!({"sheet": 0}))]);
+        assert!(failure.is_none(), "`{id}`: {failure:?}");
+    }
+}