Factor out callback in ellama-chat to a separate named

[tvraman]

function so it can be advised or extended by external packages like Emacspeak.

[Stebalien]

Are you sure you don't want a hook instead? This function is only the default behavior.

[s-kostyaev]

I think hook will be better.

[tvraman]

I think eventually we want both.

Starting from desired behavior:

1. The spoken/auditory feedback needs to be specific to a given type of interaction, so for chat you want to speak the response, for code-review or completion, the desired behavior will be different.

   2. So let's experiment with various approaches; addressing it via the default handler was just step 0.

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[s-kostyaev]

Let's try this approach. Thank you @tvraman