Refactor menu rendering and asset registry structure

- Updated SoftwareRenderer to incorporate MenuHeaderBand for handling spear variant menus and improved backdrop drawing.
- Refactored asset registry imports to organize menu-related assets under a dedicated menu structure.
- Enhanced game session snapshot tests to validate menu theme restoration for spear variant games.
- Added tests for classic menu presentation module to ensure palette consistency with canonical constants.
- Implemented tests for spear asset registry to verify correct menu VGA index resolutions.
- Created unit tests for MenuHeaderBand to validate functionality in rendering menu headers and sidebars.
- Adjusted HUD module imports to align with new menu structure.

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/test/menu/menu_manager_test.dart

@@ -159,6 +159,23 @@ void main() {
       expect(manager.transitionEffect, WolfTransitionEffect.none);
       expect(manager.activeMenu, WolfMenuScreen.difficultySelect);
     });
+
+    test('spear variant main menu omits READ THIS row', () {
+      final manager = MenuManager();
+
+      manager.beginSelectionFlow(
+        gameCount: 1,
+        initialGameIsSpear: true,
+      );
+      manager.showMainMenu(hasResumableGame: false, hasLoadableSave: true);
+
+      expect(
+        manager.mainMenuEntries.any(
+          (entry) => entry.action == WolfMenuMainAction.readThis,
+        ),
+        isFalse,
+      );
+    });
   });
 }