fix(tui): preserve modal focus across dialog replacement (#36656)

Co-authored-by: Simon Klee <52795+simonklee@users.noreply.github.com>
Co-authored-by: opencode-agent[bot] <opencode-agent[bot]@users.noreply.github.com>

packages/tui/src/ui/dialog.tsx

@@ -90,6 +90,7 @@ function init() {
   let focus: Renderable | null
   function refocus() {
     setTimeout(() => {
+      if (store.stack.length > 0) return
       if (!focus) return
       if (focus.isDestroyed) return
       function find(item: Renderable) {