feat(core): add base entity transform and physics integration

core/include/vf/Entity.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <cstdint>
+#include "World.h"
+#include "Math.h"
+#include "Physics.h"
+#include "Pathfind.h"
+
+namespace vf {
+
+enum class MobState : uint8_t {
+    Wander = 0,
+    Chase = 1,
+};
+
+struct Mob {
+    Vec3 position;   // feet centre (bottom of the collision box)
+    Vec3 velocity;
+    float width = 0.6f;
+    float height = 1.8f;
+    bool onGround = false;
+    MobState state = MobState::Wander;
+    uint32_t rng = 0x2545f491u;   // deterministic wander stream
+    Vec3 wanderDir;
+};
+
+struct MobConfig {
+    float moveSpeed = 3.2f;
+    float gravity = 26.0f;
+    float maxFallSpeed = 55.0f;
+    float chaseRadius = 12.0f;   // start chasing inside this range
+    float loseRadius = 16.0f;    // give up chasing beyond this (hysteresis)
+    PathConfig path;
+};
+
+Aabb mobBox(const Mob& mob);
+Vec3i mobFeetCell(const Mob& mob);
+
+// One physics tick: applies the horizontal wish direction and gravity, then
+// resolves AABB collisions against solid voxels axis by axis (move and slide).
+void stepMob(const World& world, Mob& mob, const Vec3& wishDir, const MobConfig& config, float dt);
+
+// State machine driving the mob. Chases when the target is within range and a
+// path exists, otherwise wanders. Updates mob.state and returns the horizontal
+// wish direction to hand to stepMob.
+Vec3 updateMobBrain(const World& world, Mob& mob, const Vec3& targetPos, const MobConfig& config);
+
+} // namespace vf