Make Focus show important details

Nobody has claimed this yet.

# Feature request

Focusing on an element should provide more details than before. For example let us say I want to know more about the inner structure of the CodeCharta "SonarImporter" and focus on it. The result is this:

It is bigger, yes, but where are the folders of the inner structure? By comparison this is the result of using `modify` to set the root to the sonarimporter:

This shows a lot more details. If I reset the root again to src/main/kotlin/... I could see even more details:

## Description

As an auditor, I want the focus to show the details of whatever I focus on.

## Acceptance criteria
Make focus work the same way that --set-root does for `modify`:

- On focus, show a squarified tree map for focused folder, with floor labels and everything

## Assumptions & Exclusions

## Development notes (optional Task Breakdown)
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## Open questions

Start by tracing the existing focus behavior and compare it with the modify flow for --set-root. Determine how the focused folder is currently rendered and how the set-root view supplies floor labels and the squarified tree map. Done means focusing a folder presents the same level of detail as setting it as the root, including its inner folders and floor labels.

Written by the indexing model from the issue text.