feat: selecting Compare from item popup in Compare panel will set new initialItemId

[FlaminSarge]

Text on button changes to New Compare when this will occur

Adding items to Compare session from main inventory now requires selecting Compare on Item Popup instead of being one click

First commit in this PR has the behavior of fully removing the existing compare session and starting a new one with the selected item.

[bhollis]

I can see that you no longer can add a matching item by just clicking on it - you have to click "Compare" or hit C. That's fine, though it may confuse folks used to the old workflow.

Hitting "Compare" on a non-matching item gives the same old error about not being comparable - it doesn't start a new compare session, and the label doesn't change. Am I missing something?

[FlaminSarge]

Hitting "Compare" on a non-matching item gives the same old error about not being comparable - it doesn't start a new compare session, and the label doesn't change. Am I missing something?

I don't think either of the two versions of this PR (first commit starting new session or second commit setting new initialItemId but preserving session) had this behavior, but I think it's worth adding as the behavior when selecting a non-matching item. I'm leaving this in draft until I can implement that.