chore: remove Unity AI Toolkit packages to fix enum warnings

- Remove com.unity.ai.assistant, com.unity.ai.generators, com.unity.ai.inference
- Update packages-lock.json
- Additional Phase 19 visual polish updates

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

unity-client/Assets/Scripts/Visual/VisualEffectsManager.cs

@@ -222,6 +222,55 @@ namespace TheIsland.Visual
             return Sprite.Create(tex, new Rect(0, 0, size, size), new Vector2(0.5f, 0.5f));
         }
 
+        public void SpawnFootstepDust(Vector3 position)
+        {
+            var dust = new GameObject("FootstepDust");
+            dust.transform.position = position;
+            var sprite = dust.AddComponent<SpriteRenderer>();
+            sprite.sprite = CreateDustSprite();
+            sprite.color = new Color(0.9f, 0.8f, 0.6f, 0.4f);
+            sprite.sortingOrder = 5; // Behind agents usually or just low
+            dust.AddComponent<Billboard>();
+            StartCoroutine(AnimateDust(dust));
+        }
+
+        private Sprite CreateDustSprite()
+        {
+            int size = 16;
+            Texture2D tex = new Texture2D(size, size);
+            for (int y = 0; y < size; y++)
+            {
+                for (int x = 0; x < size; x++)
+                {
+                    float d = Vector2.Distance(new Vector2(x, y), new Vector2(size / 2f, size / 2f)) / (size / 2f);
+                    float alpha = Mathf.Max(0, 1.0f - d);
+                    tex.SetPixel(x, y, new Color(1, 1, 1, alpha * alpha));
+                }
+            }
+            tex.Apply();
+            return Sprite.Create(tex, new Rect(0, 0, size, size), new Vector2(0.5f, 0.5f));
+        }
+
+        private IEnumerator AnimateDust(GameObject dust)
+        {
+            float elapsed = 0;
+            float duration = 0.8f;
+            Vector3 startScale = Vector3.one * 0.2f;
+            Vector3 endScale = Vector3.one * 1.5f;
+            var sprite = dust.GetComponent<SpriteRenderer>();
+            
+            while (elapsed < duration)
+            {
+                elapsed += Time.deltaTime;
+                float t = elapsed / duration;
+                dust.transform.localScale = Vector3.Lerp(startScale, endScale, t);
+                sprite.color = new Color(0.9f, 0.8f, 0.6f, 0.4f * (1f - t));
+                dust.transform.position += Vector3.up * Time.deltaTime * 0.5f;
+                yield return null;
+            }
+            Destroy(dust);
+        }
+
         private IEnumerator AnimateFirefly(GameObject firefly)
         {
             Vector3 startPos = firefly.transform.position;