Now that the object table holds ALL entities (creatures, NPCs, world objects),
filtering ObjectAdded/Updated/Removed to the 18 shortcut guids prevents the bar
from thrashing on every creature spawn in a busy zone.
Also subscribes to ObjectRemoved so a despawned/traded-away item clears its slot
(matching retail gmToolbarUI::SetDelayedShortcutNum's deferred-bind contract).
Four new unit tests (iconIds spy pattern) verify: non-shortcut ObjectAdded/Removed
do NOT invoke Populate; shortcut ObjectAdded deferred-binds; shortcut ObjectRemoved
clears the slot. 2671 tests, 4 skipped, 0 failures.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>