When the agent is writing group and is in progress, the next group shows not hint

### What happened

When I press the `n` button when the next group is still written, I must get some sort of an indication that dude, this is being written, wait etc. There is none, we need to fix this.

### Version

0.0.9

### Platform

macOS

### Which editor's theme

_No response_

### Where deck looked

```text

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### Did the window close on its own?

```text

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Reproduce the issue in version 0.0.9 on macOS by pressing `n` while the next group is still being written. Start by locating the `n` key handling and the group-writing progress state; done means the interface visibly indicates that the next group is still being written and tells the user to wait.

Written by the indexing model from the issue text.