noExplode makes Cannon/DGun partially spherical

These weapon types get a spherical range mechanics when `noExplode` is set but everything else (GUI, unit AI such as targeting etc) still behaves as if they're ballistic. Range circle still expands (instead of shrinking) when placed on a hill, a ship will still shoot both seafloor and air targets even if it can't reach them, etc.

Start by tracing how noExplode is handled for Cannon and DGun across range visualization, unit targeting, and terrain or air reachability. Done means these systems consistently use spherical range mechanics instead of retaining ballistic behavior.

Written by the indexing model from the issue text.