fix(items): use retail cylinder range for loot windows

Keep external-container visibility tied to the signed surface gap between the player and container physics cylinders, matching gmExternalContainerUI's authored UseRadius range watcher. This prevents a valid ViewContents response from being closed at ACE's natural approach endpoint.

Port Position::cylinder_distance and ACCWeenieObject::ObjectsInRange into Core with conformance coverage for 3-D separation, overlap, mode precedence, and inclusive boundaries.

Release build succeeds and all 5,895 tests pass with five intentional skips.

Co-authored-by: OpenAI Codex <codex@openai.com>

src/AcDream.Core/Physics/ObjectRangeMath.cs

@@ -0,0 +1,53 @@
+using System.Numerics;
+using AcDream.Core.Physics.Motion;
+
+namespace AcDream.Core.Physics;
+
+/// <summary>
+/// Retail object-range predicate used by <c>CPlayerSystem</c> range handlers.
+/// Port of <c>ACCWeenieObject::ObjectsInRange @ 0x0058C1A0</c>.
+/// </summary>
+public static class ObjectRangeMath
+{
+    /// <summary>
+    /// Tests two live physics objects against a caller-supplied range. Retail
+    /// gives <paramref name="ignoreZDelta"/> precedence; otherwise
+    /// <paramref name="useRadii"/> selects cylinder-gap distance instead of
+    /// ordinary center distance.
+    /// </summary>
+    public static bool ObjectsInRange(
+        Vector3 firstPosition,
+        float firstRadius,
+        float firstHeight,
+        Vector3 secondPosition,
+        float secondRadius,
+        float secondHeight,
+        double range,
+        bool useRadii,
+        bool ignoreZDelta)
+    {
+        double distance;
+        if (ignoreZDelta)
+        {
+            double dx = secondPosition.X - firstPosition.X;
+            double dy = secondPosition.Y - firstPosition.Y;
+            distance = Math.Sqrt(dx * dx + dy * dy);
+        }
+        else if (useRadii)
+        {
+            distance = MoveToMath.CylinderDistance(
+                firstRadius,
+                firstHeight,
+                firstPosition,
+                secondRadius,
+                secondHeight,
+                secondPosition);
+        }
+        else
+        {
+            distance = Vector3.Distance(firstPosition, secondPosition);
+        }
+
+        return distance <= range;
+    }
+}