Fix keyboard handling for Escape and Ctrl+Backspace in crumble

[Raycosine]

Both were not calling the methods, so the shortcuts didn’t work.

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[Strilanc]

Well that's embarrassing.

Thanks for catching it.

[Strilanc]

Ah the error is just that the version built into stim's C++ source is desynced from the source. I can handle that.

[Strilanc]

Can't push to your branch so I moved this to #1038 and will merge from there.

[Raycosine]

Can't push to your branch so I moved this to #1038 and will merge from there.

Thanks a lot for handling the extra steps!