style: narrow Optionals for basedpyright diff gate

QLayout.itemAt/QWidget.layout return Optionals; pyright cannot narrow
across repeated method calls, so hold them in locals before use in
tighten_column, _apply_collapsed and _set_visible.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/aare/gui/widgets/title_label.py

@@ -16,10 +16,12 @@ def tighten_column(layout: QLayout) -> None:
     """
     layout.setSpacing(PANEL_VSPACING)
     for i in range(layout.count()):
-        w = layout.itemAt(i).widget()
-        if w is not None and w.layout() is not None:
-            m = w.layout().contentsMargins()
-            w.layout().setContentsMargins(m.left(), PANEL_VMARGIN, m.right(), PANEL_VMARGIN)
+        item = layout.itemAt(i)
+        widget = item.widget() if item is not None else None
+        child_layout = widget.layout() if widget is not None else None
+        if child_layout is not None:
+            m = child_layout.contentsMargins()
+            child_layout.setContentsMargins(m.left(), PANEL_VMARGIN, m.right(), PANEL_VMARGIN)
 
 
 class TitleLabel(QLabel):
@@ -91,9 +93,10 @@ class TitleLabel(QLabel):
 
     def _apply_collapsed(self) -> None:
         parent = self.parentWidget()
-        if parent is None or parent.layout() is None:
+        parent_layout = parent.layout() if parent is not None else None
+        if parent_layout is None:
             return
-        self._set_visible(parent.layout(), not self._collapsed)
+        self._set_visible(parent_layout, not self._collapsed)
         self.toggle_button.setText("+" if self._collapsed else "−")
         self.toggle_button.setToolTip("Restore panel" if self._collapsed else "Minimise panel")
 
@@ -101,9 +104,12 @@ class TitleLabel(QLabel):
         # Recursive: panels like SamcamPanel nest sub-layouts via addLayout.
         for i in range(layout.count()):
             item = layout.itemAt(i)
+            if item is None:
+                continue
             widget = item.widget()
+            child_layout = item.layout()
             if widget is not None:
                 if widget is not self:
                     widget.setVisible(visible)
-            elif item.layout() is not None:
-                self._set_visible(item.layout(), visible)
+            elif child_layout is not None:
+                self._set_visible(child_layout, visible)