Allow disconnecting and reconnecting parent-child relationships

### Problem

When building a large hierarchy, users often realize that an intermediate node was forgotten.

Example:

Current structure:

```text
Grandfather
│
└── Ahmed
└── Mohamed
```

Later, the user realizes that another person should exist between them.

Desired structure:

```text
Grandfather
│
└── Father
│
└── Ahmed
│
└── Mohamed
```

Currently, the only solution is to manually rebuild part of the hierarchy.

### Proposed Solution

Allow users to disconnect and reconnect relationships independently from the nodes.

Possible workflow:

1. Select the connector (edge) between two nodes.
2. Disconnect or remove the relationship.
3. Insert a new node.
4. Connect the new node to both existing nodes.

Or even better:

* Drag an existing connector endpoint onto another node to reconnect it.

### Benefits

* Makes editing existing hierarchies much easier.
* Eliminates unnecessary rebuilding.
* Very useful for genealogy trees and organization charts.
* Allows flexible restructuring of large mind maps.

No file, test, or entry point is named in the issue. Start by locating the mindmap connector and node-editing interactions, then clarify whether disconnect/reconnect or endpoint dragging is required; done means relationships can be restructured without rebuilding the existing hierarchy.

Written by the indexing model from the issue text.