Scope tracked item updates to current menu and skip when page inactive

- Store tracked items per-menu instead of one global list
- UpdateTrackedItems and IncrementCurrentValue only process the
  currently visible menu's items
- Skip all updates when the MJ page isn't active (pageActiveState)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: vanillamc