Collaborative chat models manager

[brichet]

It may be interesting to have a manager of collaborative chat models, to dissociate the model from the widget.

Problems

• notifications (after Notifications for unread messages #43) will be enabled only if a widget is open for the chat.
• moving a widget from main area to the side panel (and vice versa) recreates a model from scratch. Moving the widget uses app commands, and there is no way to pass on complex arguments (model for instance).

Proposed Solution

Add a model manager, that would allow having a model running without any widget. That way we could:

• reference it when moving a widget from one area to an other
• add a context menu command to a chat file to enable notification without any opened widget
• add the manager to the running session panel, to let user manage its running models

[brichet]

Related comments:

• Notifications for unread messages #43 (comment)
• Notifications for unread messages #43 (comment)