feat(creatures): refine pig movement physics

Add movement constants for pigs and switch deceleration to per-axis friction so creatures stop naturally. Extend wander boost duration for smoother behavior.

include/Cubed/gameplay/creatures/pig.hpp

@@ -3,4 +3,11 @@
 namespace Cubed {
 struct PigTag {};
 
+namespace PigDefaults {
+constexpr float MAX_SPEED = 0.1f;     // tiles/tick → 2 tiles/sec
+constexpr float ACCELERATION = 0.01f; // ~10 ticks (0.5s) to reach full speed
+constexpr float DECELERATION = 0.02f; // ~5 ticks (0.25s) to stop
+constexpr float GRAVITY = 1.0f;       // ≈20 tiles/s², close to the player
+} // namespace PigDefaults
+
 } // namespace Cubed

include/Cubed/gameplay/systems/physical_system.hpp

@@ -1,14 +1,12 @@
 #pragma once
 #include "Cubed/gameplay/ecs/movement.hpp"
-#include "Cubed/gameplay/ecs/transform.hpp"
 
 #include <entt/entt.hpp>
 namespace Cubed {
 class ServerWorld;
 class PhysicalSystem {
 public:
-    static glm::vec3 get_move_distance(const Direction& d,
-                                       const TickVelocity& v);
+    static glm::vec3 get_move_distance(const TickVelocity& v);
 
     static void update(ServerWorld& world, entt::registry& registry);