Fix record picker search results clearing on add

The update/2 callback unconditionally reset the query and results to empty
on every parent re-render. Changed to assign_new/3 so search state persists
when the parent updates the record set after adding a record.

lib/music_library_web/live/record_set_live/record_picker.ex

@@ -140,9 +140,9 @@ defmodule MusicLibraryWeb.RecordSetLive.RecordPicker do
     {:ok,
      socket
      |> assign(assigns)
-     |> assign(:query, "")
+     |> assign_new(:query, fn -> "" end)
-     |> assign(:collected_results, [])
+     |> assign_new(:collected_results, fn -> [] end)
-     |> assign(:wishlisted_results, [])
+     |> assign_new(:wishlisted_results, fn -> [] end)
      |> assign(:existing_record_ids, existing_record_ids)}
   end