Refactor/workspace layout controller (#7768)

* refactor(activity): extract workspace layout into WorkspaceLayoutController

Move the Home button workspace layout responsibilities (_findBlocks,
repositionBlocks, setHomeContainers, _isFirstHomeClick toggle) out of
activity.js into js/activity/workspace-layout-controller.js, following
the same controller-extraction pattern used for GridController,
SearchController and SelectionController. activity.js now instantiates
the controller and keeps thin delegation stubs so existing callers are
unaffected.

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

* test(workspace-layout-controller): add behavioral test coverage

Cover setup/wiring, findBlocks, the row/column _findBlocks toggle,
repositionBlocks breakpoint handling, resize delegation,
setHomeContainers, turtle reset behavior, and edge cases such as
empty, single-block and large workspaces.

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

* fix(workspace-layout-controller): guard findBlocks against a missing helpfulWheelDiv

document.getElementById("helpfulWheelDiv") can return null; accessing
.style on it would throw. The pre-extraction code had the same gap,
so guard it now that the code is being touched.

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

* refactor(workspace-layout-controller): bind delegation stubs and reduce test duplication

Use controller.method.bind(controller) instead of arrow-function
wrappers for the activity-level delegation stubs, and add a
setupActivity() test helper to collapse the repeated
makeActivity()+setupWorkspaceLayoutController() pairing across the
suite. Also correct a misleading comment (the DOM lookup isn't
cached, it's just done once).

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

---------

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

Author: vanshika2720

js/__tests__/activity_toolbar_integration.test.js

@@ -97,6 +97,7 @@ const loadActivityClass = () => {
             helpfulSearchDiv: null
         })),
         setupSearchController: jest.fn(),
+        setupWorkspaceLayoutController: jest.fn(),
         hideDOMLabel: jest.fn(),
         setupActivityRecorder: jest.fn(),
         setupActivityAbcParser: jest.fn(),