fix(apps): make a covered elicitation dialog inert

Only the top modal owned the focus trap, but every lower `Modal.Content`
remained an exposed `aria-modal` dialog with reachable controls and a live
iframe — so browse navigation could land in a dialog that is visually covered
and that itself claims the rest of the page is inert.

Non-top contents are now `inert`: out of the accessibility tree and out of
focus order, without unmounting, so each app keeps its bridge and its handshake
and is live the moment it becomes top.

Signed-off-by: cliffhall <cliff@futurescale.com>

clients/web/src/components/elements/AppElicitation/AppElicitationHost.test.tsx

@@ -216,6 +216,12 @@ describe("AppElicitationHost (#1854)", () => {
     await flushAsync();
     expect(screen.getAllByTestId("app-elicitation")).toHaveLength(2);
 
+    // The covered dialog is inert: out of the a11y tree and out of focus
+    // order, but still mounted — its app keeps its bridge and handshake.
+    const [lower, top] = screen.getAllByTestId("app-elicitation");
+    expect(lower.hasAttribute("inert")).toBe(true);
+    expect(top.hasAttribute("inert")).toBe(false);
+
     await user.keyboard("{Escape}");
     // Exactly one request is dismissed — the topmost, which is the last one.
     expect(onFail).toHaveBeenCalledTimes(1);

clients/web/src/components/elements/AppElicitation/AppElicitationHost.tsx

@@ -253,6 +253,13 @@ function AppElicitationFrame({
           only the request id tells those two dialogs apart — for
           `landmark-unique` and for anyone navigating by screen reader. */}
       <Modal.Content
+        // A lower dialog is visually covered but would otherwise stay an
+        // exposed `aria-modal` dialog with reachable controls and an iframe —
+        // so browse navigation could land in a dialog that itself claims the
+        // rest of the page is inert. `inert` takes it out of the a11y tree and
+        // out of focus order WITHOUT unmounting, so its app keeps its bridge
+        // and its handshake and is live the moment it becomes top.
+        inert={!isTop}
         aria-label={`Elicitation ${entry.requestId} — ${entry.params.message} — rendered by ${entry.resourceUri}`}
         data-app-elicitation-status={status}
         data-testid="app-elicitation"