Another window of the same app. There is one last state per app, not per window:
the menu bar pairs, the old window is removed, the new one is added with numbers
after the largest that stayed, and the header names the new window.
== read title=One
a standard window One
.b button Go
c menu bar
.d File
== want
Window: "One", App: App.
0 standard window One
	1 button Go
2 menu bar
	3 File

== read title=Two
w standard window Two
.x text Hello
c menu bar
.d File
== want
<HEADER>
IDs of elements that went away: 0-1
+4 standard window Two
+	5 text Hello
== read title=Two renamed
w standard window Two
.x text Hello
c menu bar
.d File
== want
Nothing changed in window "Two renamed" since the last read.
== end
