Feat: Replace space by "-" (or something like "->" before children space name to make list of space more user freindly

## at present

The children space name have a space before the name. It is not easy to understand is it a children space.

## Expected

Show something like ` ` or `-` or ``->` or `=>` before name of children space name.

Start by locating the Rust entry point that formats the list of spaces and inspect how child space names are displayed. Confirm which marker is preferred, then verify that child entries are visually distinguishable from parent entries in the command output.

Written by the indexing model from the issue text.