Simplify D2Selection lobby option initialization

[evgeniysergeev]

D2Selection currently stores world and info, then lazily initializes SingleSelection through an initialized flag in Add and Combine.

This appears unnecessary: D2Selection is a world trait, and world.LobbyInfo.GlobalSettings is already available when the trait is constructed. The singleselection lobby option can be read directly in the constructor.

Suggested cleanup:

public D2Selection(World world, D2SelectionInfo info)
{
	SingleSelection = world.LobbyInfo.GlobalSettings.OptionOrDefault("singleselection", info.CheckboxEnabled);
}

Then remove:

• readonly D2SelectionInfo info
• readonly World world
• bool initialized
• Init()
• Init() calls from Add and Combine

Acceptance criteria:

• Single-selection behavior remains unchanged.
• The singleselection lobby option still controls SingleSelection.
• No unnecessary lazy initialization state remains in D2Selection.
• Project builds successfully.