UI: Stats tracker can forget history

Background: StatTrackers keep historical stats metrics for allocations or clients. They are stored in a global service so even if you leave a page and return, the historical stats still exist.

Problem: Sometimes that historical gets deleted

Steps to Reproduce:

1. Go to an allocation, let stats collect
2. Go to a client via the sidebar, let stats collect
3. Use the browser back button to return to the allocation, observe that no stats are remembered

Reproduce the allocation-to-client navigation sequence and the browser back-button return described in the issue. Start by tracing how UI StatTrackers are stored in the global service across page changes; done means historical stats remain visible when returning to the allocation.

Written by the indexing model from the issue text.