fix(core): improve view robustness and axis management

`records_display` now returns `None` for out-of-bounds columns.

Added `try_axis_of` to `View` for non-panicking axis retrieval.

`cycle_axis` now uses `try_axis_of` to avoid panicking on unknown
categories.

Add regression tests for out-of-bounds access and unknown category cycling.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-26B-A4B-it-GGUF:UD-Q5_K_XL)

crates/improvise-core/src/view/layout.rs

@@ -182,11 +182,15 @@ impl GridLayout {
     }
 
     /// Get the display string for the cell at (row, col) in records mode.
-    /// Returns None for normal (non-records) layouts.
+    /// Returns None for normal (non-records) layouts and for out-of-bounds
+    /// rows/columns (symmetric with `cell_key`).
     pub fn records_display(&self, row: usize, col: usize) -> Option<String> {
         let records = self.records.as_ref()?;
         let record = records.get(row)?;
         let col_item = self.col_label(col);
+        if col_item.is_empty() {
+            return None;
+        }
         if col_item == "Value" {
             Some(record.1.to_string())
         } else {
@@ -806,6 +810,23 @@ mod tests {
         assert_eq!(last_value, "999", "new record should be the last row");
     }
 
+    /// Regression test for improvise-byz: `records_display` for an
+    /// out-of-bounds column called `col_label(col)`, which returns `""`;
+    /// `""` fails the `== "Value"` check, gets looked up as a category name
+    /// in the record (never found), and the function returned `Some("")` —
+    /// masking view/data mismatches. It must return `None`, symmetric with
+    /// `cell_key`, which explicitly returns `None` for an empty col label.
+    #[test]
+    fn records_display_out_of_bounds_col_returns_none() {
+        let mut wb = records_workbook();
+        let v = wb.active_view_mut();
+        v.set_axis("_Index", Axis::Row);
+        v.set_axis("_Dim", Axis::Column);
+        let layout = GridLayout::new(&wb.model, wb.active_view());
+        assert!(layout.is_records_mode());
+        assert_eq!(layout.records_display(0, layout.col_count()), None);
+    }
+
     fn coord(pairs: &[(&str, &str)]) -> CellKey {
         CellKey::new(
             pairs

crates/improvise-core/src/view/types.rs

@@ -111,13 +111,28 @@ impl View {
         }
     }
 
+    /// Axis assignment for a registered category.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `cat_name` is not registered with this view. Registration
+    /// is guaranteed for every model category: `Workbook::new`,
+    /// `Workbook::add_category`, `Workbook::add_label_category`, and
+    /// `Workbook::create_view` all call `View::on_category_added` for every
+    /// view, so any name obtained from `Model::categories` or from this
+    /// view's own `category_axes` is safe. Use [`View::try_axis_of`] when
+    /// the name comes from anywhere else.
     pub fn axis_of(&self, cat_name: &str) -> Axis {
-        *self
-            .category_axes
-            .get(cat_name)
+        self.try_axis_of(cat_name)
             .expect("axis_of called for category not registered with this view")
     }
 
+    /// Non-panicking variant of [`View::axis_of`]: returns `None` when the
+    /// category is not registered with this view.
+    pub fn try_axis_of(&self, cat_name: &str) -> Option<Axis> {
+        self.category_axes.get(cat_name).copied()
+    }
+
     pub fn categories_on(&self, axis: Axis) -> Vec<&str> {
         self.category_axes
             .iter()
@@ -208,9 +223,11 @@ impl View {
         self.col_offset = 0;
     }
 
-    /// Cycle axis for a category: Row → Column → Page → None → Row
+    /// Cycle axis for a category: Row → Column → Page → None → Row.
+    /// No-op for an unregistered category, consistent with `set_axis`.
     pub fn cycle_axis(&mut self, cat_name: &str) {
-        let next = match self.axis_of(cat_name) {
+        if let Some(current) = self.try_axis_of(cat_name) {
+            let next = match current {
                 Axis::Row => Axis::Column,
                 Axis::Column => Axis::Page,
                 Axis::Page => Axis::None,
@@ -222,6 +239,7 @@ impl View {
             self.col_offset = 0;
         }
     }
+}
 
 #[cfg(test)]
 mod tests {
@@ -305,6 +323,31 @@ mod tests {
         v.axis_of("Ghost");
     }
 
+    /// Regression test for improvise-t8s: `cycle_axis` panicked (via the
+    /// `expect` in `axis_of`) when given a category not registered with the
+    /// view, while `set_axis` silently no-ops on the same input. `cycle_axis`
+    /// now goes through `try_axis_of` and no-ops on unknown categories,
+    /// consistent with `set_axis`.
+    #[test]
+    fn cycle_axis_unknown_category_is_noop() {
+        let mut v = view_with_cats(&["Region"]);
+        v.cycle_axis("Ghost");
+        assert_eq!(v.axis_of("Region"), Axis::Row);
+        assert_eq!(v.try_axis_of("Ghost"), None);
+    }
+
+    #[test]
+    fn try_axis_of_known_category_returns_some() {
+        let v = view_with_cats(&["Region"]);
+        assert_eq!(v.try_axis_of("Region"), Some(Axis::Row));
+    }
+
+    #[test]
+    fn try_axis_of_unknown_category_returns_none() {
+        let v = View::new("Test");
+        assert_eq!(v.try_axis_of("Ghost"), None);
+    }
+
     #[test]
     fn page_selection_set_and_get() {
         let mut v = view_with_cats(&["Region", "Product", "Time"]);