Add a file menu option to "Ask Navie about this file"

[kgilpin]

When Navie is open, I can right-click a code file to "Add files to Navie Context":

However, if a Navie chat is not open, there's no Navie option in the context menu:

I suggest that if a Navie chat is not open, we add a menu option "AppMap: Ask Navie about this file" that will open a new Navie chat with the file added as a pinned file.