ZK nanoturret decal reveals death outside LoS

Repro:

1) `/give staticcon ` and scout it but then leave so it's in the fog. No radar or LoS coverage.
2) notice that it leaves a decal on the ground.
3) kill it without scouting (tacnuke it, give hostile units to Gaia, etc).
4) notice that the building decal has decayed and is gone (may take a moment for the death explosion decal to expire too to see it).


Reproduce the `/give staticcon ` scenario with the enemy hidden in fog and no radar or LoS, then kill it by tacnuke or Gaia control. Trace the building and death decal handling and verify that killing an unobserved enemy does not reveal its death through a decal change or disappearance.

Written by the indexing model from the issue text.