Add TownSquare scene assets, resource production docs, and model pipeline updates.

Bring in plaza props/prefabs, ZhaoYun source GLB, design originals, and Hunyuan/Blender tooling used to produce them.

Co-authored-by: Cursor <cursoragent@cursor.com>

AIClient/Assets/HotUpdate/Scripts/GroundSit.cs

@@ -0,0 +1,64 @@
+using UnityEngine;
+
+namespace HotUpdate
+{
+    /// <summary>
+    /// 用地表 MeshCollider 的碰撞高度作为放置 Y。原点在底面中点的物件直接用该值。
+    /// </summary>
+    public static class GroundSit
+    {
+        const float RayStartY = 80f;
+        const float RayLength = 160f;
+
+        public static float Height(Vector3 xz, Transform searchRoot = null, float fallback = 0f)
+        {
+            Physics.SyncTransforms();
+            var ray = new Ray(new Vector3(xz.x, RayStartY, xz.z), Vector3.down);
+            var bestDist = float.MaxValue;
+            var y = fallback;
+            var hitAny = false;
+
+            foreach (var col in Collect(searchRoot))
+            {
+                if (col == null || !col.enabled) continue;
+                if (!IsGroundCollider(col)) continue;
+                if (!col.Raycast(ray, out var hit, RayLength)) continue;
+                if (hit.distance >= bestDist) continue;
+                bestDist = hit.distance;
+                y = hit.point.y;
+                hitAny = true;
+            }
+
+            if (hitAny) return y;
+
+            foreach (var col in Collect(searchRoot))
+            {
+                if (col == null || !col.enabled) continue;
+                if (!col.Raycast(ray, out var hit, RayLength)) continue;
+                if (hit.distance >= bestDist) continue;
+                bestDist = hit.distance;
+                y = hit.point.y;
+                hitAny = true;
+            }
+
+            return hitAny ? y : fallback;
+        }
+
+        static MeshCollider[] Collect(Transform searchRoot)
+        {
+            if (searchRoot != null)
+                return searchRoot.GetComponentsInChildren<MeshCollider>();
+            return Object.FindObjectsByType<MeshCollider>(FindObjectsSortMode.None);
+        }
+
+        static bool IsGroundCollider(MeshCollider col)
+        {
+            for (var t = col.transform; t != null; t = t.parent)
+            {
+                if (t.name.IndexOf("ground", System.StringComparison.OrdinalIgnoreCase) >= 0)
+                    return true;
+            }
+            return false;
+        }
+    }
+}