Ensure floating dockable windows resize content

HISTORY.md

@@ -18,6 +18,13 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 -->
 
+## 0.2.271 - 2025-09-11
+
+- Prevent dockable floating containers from shrinking to their original size
+  so snapped-out diagrams expand when the window is resized or maximized.
+- Add regression coverage ensuring dockable floating content tracks window
+  size changes after resizing.
+
 ## 0.2.270 - 2025-09-10
 
 - Restore standard decorations on detached notebooks so floating windows offer

gui/utils/dockable_diagram_window.py

@@ -55,6 +55,15 @@ def _ensure_float_container(self, win: tk.Toplevel) -> ttk.Frame:
             container = ttk.Frame(win)
             container.pack(expand=True, fill="both")
             self._float_container = container
+        else:
+            try:
+                container.pack_configure(expand=True, fill="both")
+            except tk.TclError:
+                container.pack(expand=True, fill="both")
+        try:
+            container.pack_propagate(False)
+        except tk.TclError:
+            pass
         return container
 
     def _release_from_geometry(self) -> None: