feat(core): add voxel raycasting for block targeting

core/include/vf/Raycast.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "World.h"
+#include "Math.h"
+
+namespace vf {
+
+struct RaycastHit {
+    bool hit = false;
+    Vec3i block;    // solid voxel that was struck
+    Vec3i normal;   // face normal pointing back toward the ray origin
+    float distance = 0.0f;
+};
+
+// Amanatides and Woo voxel traversal. Steps the grid from `origin` along
+// `direction` up to `maxDistance` world units, stopping at the first solid
+// voxel. `normal` gives the entered face, so `block + normal` is the empty
+// neighbour where a new block can be placed.
+RaycastHit raycastVoxels(const World& world, const Vec3& origin, const Vec3& direction,
+                         float maxDistance);
+
+} // namespace vf