Tapping the queue button from /now-playing crashed with
NavigatorState._debugCheckDuplicatedPageKeys. Root cause: when I
moved /now-playing out of the ShellRoute earlier, /queue was left
inside the shell. Pushing /queue while /now-playing was on top
made go_router try to mount a second ShellRoute instance under the
existing one — both shells got the same page key.
Move /queue out of the ShellRoute too, sibling to /now-playing.
Shell stays mounted (with whatever child it had) underneath both
top-level routes; pop from /queue returns to /now-playing or the
shell's previous child as appropriate.
bvandeusen
c1df2af992