Refactor UpdateViewModel to use new UpdateState

The user wants me to update the UpdateViewModel.swift file to:

1. Use the new UpdateState exclusively (the enum defined at the top)
2. Rename state2 to state
3. Remove the old state property (which is of type State)

Looking at the file, I can see:

• There's a new UpdateState enum (lines 16-63)
• The class has @Published var state2: UpdateState = .idle (line 66)
• The class has the old @Published var state: State = .idle (line 68)
• There are also progress, details, and error properties that seem to be associated with the old state system
• There's an old State enum (lines 73-84)
• There are various computed properties that use the old state property

I need to:

1. Remove the old State enum (lines 73-84)
2. Remove the old @Published var state: State = .idle (line 68)
3. Rename state2 to state
4. Remove or update the properties that were used with the old state system (progress, details, error)
5. Update all the computed properties to work with the new UpdateState

Let me plan this carefully. The computed properties like stateTooltip, text, iconName, iconColor, backgroundColor, and foregroundColor all switch on the old state. I need to update them to switch on the new UpdateState.

Looking at the new UpdateState, it has associated values for various cases, so I'll need to extract those when needed in the computed properties.

Let me start by creating a TODO list and then make the changes.