Kitti3 should complain if Kitty is not installed

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i3's exec command is happy enough regardless of what you ask it to execute, such that even if Kitty is not installed on a user's system the return status of the IPC exec request sent by spawn will indicate success.

The entrypoint cli function could perhaps do a quick check during startup (akin to $ which kitty) and complain if Kitty can't be resolved?

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Don't see a viable path for Kitti3 to provide this feedback to the user, given that it is itself spawned via an i3 exec_always. Hopefully most users will have enough common sense and problem solving skills to deal with this unlikely scenario.