feat(core): add cave-generation and fog tuning to Configuration

Core/Configuration.cs

@@ -23,4 +23,18 @@ public sealed class Configuration
     public int WindowHeight { get; set; } = 720;
 
     public int? Seed { get; set; } = null;
+
+    // -- Cave generation tuning --
+    public float CaveNoiseFrequency           { get; set; } = 0.03f;
+    public float CaveNoiseThreshold           { get; set; } = -0.3f;
+    public int   WormCellSize                 { get; set; } = 64;
+    public int   WormSpawnProbabilityPermille { get; set; } = 300;
+    public int   WormMaxLength                { get; set; } = 80;
+    public float WormMinRadius                { get; set; } = 1.5f;
+    public float WormMaxRadius                { get; set; } = 3.5f;
+
+    // -- Cave lighting (fog-distance darkness) --
+    public float CaveDarkStartY    { get; set; } = 72f;   // WorldConstants.SeaLevel + 8
+    public float CaveDarkEndY      { get; set; } = 32f;   // WorldConstants.SeaLevel - 32
+    public float CaveMinBrightness { get; set; } = 0.15f;
 }

VoxelEngine.Tests/ConfigurationTests.cs

@@ -54,4 +54,24 @@ public class ConfigurationTests
         Assert.Equal(800,  c2.WindowWidth);
         Assert.Equal(600,  c2.WindowHeight);
     }
+
+    [Fact]
+    public void Defaults_HaveCaveTuningConstants()
+    {
+        var c = new Configuration();
+
+        // Algorithm
+        Assert.Equal(0.03f, c.CaveNoiseFrequency);
+        Assert.Equal(-0.3f, c.CaveNoiseThreshold);
+        Assert.Equal(64,    c.WormCellSize);
+        Assert.Equal(300,   c.WormSpawnProbabilityPermille);
+        Assert.Equal(80,    c.WormMaxLength);
+        Assert.Equal(1.5f,  c.WormMinRadius);
+        Assert.Equal(3.5f,  c.WormMaxRadius);
+
+        // Lighting (fog)
+        Assert.Equal(72f,   c.CaveDarkStartY);    // SeaLevel (64) + 8
+        Assert.Equal(32f,   c.CaveDarkEndY);      // SeaLevel (64) - 32
+        Assert.Equal(0.15f, c.CaveMinBrightness);
+    }
 }