Reference list items by stable `[REDACTED]`, not array index, when the server mutates the list

Inventory actions (equip, sell, swap) addressed by array index break the instant a concurrent server action shifts the array — a drop arrives, an auto-sort runs, another panel sells something. The client sends equip(index: 4), the server resolves index 4 to a different item than what the user clicked, and you get 'sold the wrong sword' bugs that are infuriating to reproduce because they only happen when two actions land in the same tick.