Revert "config: test without terrain haze"

This reverts commit f4eb826c3a.

config.js

@@ -572,7 +572,7 @@ window.CONFIG = {
             maxAlpha: 0.55
         },
         terrainHaze: {
-            enabled: false,       // test: no terrain haze
+            enabled: true,        // terrain-distance based haze on the ground
             scaleHeightKm: 8.5,   // exponential vertical falloff
             density: 0.22,        // optical depth per world unit
             gain: 1.0,            // overall multiplier