fix: improve workspace manager navigation and sizing

frontend/src/shell/WorkspaceManager.test.tsx

@@ -70,15 +70,27 @@ beforeEach(() => {
   );
 });
 
-test("uses at least sixty percent of the viewport on desktop", () => {
+test("uses a tall viewport area and keeps the workspace content scrollable", () => {
   renderManager();
 
-  expect(screen.getByRole("dialog")).toHaveClass(
-    "h-[70vh]",
+  const dialog = screen.getByRole("dialog");
+  expect(dialog).toHaveClass(
+    "h-[86vh]",
     "w-[94vw]",
     "sm:w-[70vw]",
     "max-w-[94vw]",
   );
+  expect(screen.getByRole("main")).toHaveClass("overflow-y-auto");
+});
+
+test("offers an internal link back to the initial page", async () => {
+  const user = userEvent.setup();
+  const onClose = vi.fn();
+  renderManager(onClose);
+
+  await user.click(screen.getByRole("button", { name: "Back to main page" }));
+
+  expect(onClose).toHaveBeenCalledTimes(1);
 });
 
 test("level one explains the read-only Git sequence and the repository update button", async () => {