fix(host): harden the browser dialog against review round-2 races

- Dismissal (Escape/mask) is ignored while adoption is busy: the owner's
  in-flight createWorkspace must not land behind an apparent cancel.
- Every parent control goes inert while the nested create dialog is open
  (Modal traps no focus, so Shift-Tab/AT could close, adopt, or retarget
  underneath the child).
- Creation settlements are gated on an open-generation ref: a create that
  resolves or rejects after the flow closed (and possibly reopened) can no
  longer relist the stale target or surface its alert in the fresh dialog.
- The keyless snapshot waits for the Open button's enabled state before
  clicking — on slow runners the selection's child listing was still in
  flight and the click landed on a disabled button.

apps/web/tests/workspace-flow.snapshot.ts

@@ -202,6 +202,11 @@ it('adopts a directory through the composed in-app browse flow and lands in its
   // row's name span is stable (clicks bubble to the row button).
   fireEvent.click(await within(dialog).findByText('Documents', {}, { timeout: 10_000 }))
   fireEvent.click(await within(dialog).findByText('project', {}, { timeout: 10_000 }))
+  // Open disables while the selection's child listing is in flight; wait for
+  // the enabled state or the click lands on a dead button on slow runners.
+  await waitFor(() => {
+    expect(within(dialog).getByRole<HTMLButtonElement>('button', { name: '打开' }).disabled).toBe(false)
+  }, { timeout: 10_000 })
   fireEvent.click(within(dialog).getByRole('button', { name: '打开' }))
   await findHeroComposer()
   await waitFor(() => {