Fix landmine visualizer logic inaccuracies

[digger1213]

There were some issues with the landmine visualizer that made them calculate incorrect results compared to the behavior of landmines in-game.

• Visualizer assumed the explosion originated from the landmine's position, but landmines create the explosion 1 unit above them. This could change the outcome of raycast and distance checks.
• Visualizer assumed all players detected by OverlapSphere would take damage, but it's possible to be out of range of the landmine while still having part of the player hitbox detected by the sphere. This case now colors the visualizer line green.

With these changes, the visualizer now always matches the outcome of the explosion.

[giosuel]

I had to re-write some history, which messed up this PR. I patched this manually in d2b0ced8f600a243c1e583fe4e2ef8765245548b, thanks!