fix(ui): port exact paperdoll body selection

Resolve and sample retail's authored nine-color paperdoll click map, preserve local click coordinates, and select the stable highest-priority worn item with the player fallback. Keep targeted-use body clicks routed to self and pin both synthetic and live-DAT conformance.

Co-Authored-By: Codex <codex@openai.com>

src/AcDream.Core/Items/PaperdollSelectionPolicy.cs

@@ -0,0 +1,47 @@
+namespace AcDream.Core.Items;
+
+/// <summary>
+/// Retail paperdoll body-part selection. Ports
+/// <c>InventoryPlacement::DetermineHigherPriority @ 0x004A44B0</c> and
+/// <c>gmPaperDollUI::GetUpperInvObj @ 0x004A4750</c>.
+/// </summary>
+public static class PaperdollSelectionPolicy
+{
+    /// <summary>
+    /// Returns the visually upper equipped object covering <paramref name="bodyLocationMask"/>.
+    /// When the body part is valid but uncovered, retail returns the player object itself.
+    /// </summary>
+    public static uint GetUpperInventoryObject(
+        ClientObjectTable objects,
+        uint playerId,
+        EquipMask bodyLocationMask)
+    {
+        if (playerId == 0 || bodyLocationMask == EquipMask.None || objects.Get(playerId) is null)
+            return 0;
+
+        ClientObject? winner = null;
+        foreach (ClientObject candidate in objects.Objects)
+        {
+            if ((candidate.CurrentlyEquippedLocation & bodyLocationMask) == EquipMask.None)
+                continue;
+            if (candidate.WielderId != playerId && candidate.ContainerId != playerId)
+                continue;
+
+            if (winner is null
+                || EffectivePriority(candidate, bodyLocationMask)
+                    > EffectivePriority(winner, bodyLocationMask))
+                winner = candidate;
+        }
+
+        return winner?.ObjectId ?? playerId;
+    }
+
+    private static uint EffectivePriority(ClientObject item, EquipMask bodyLocationMask)
+    {
+        uint priority = item.Priority;
+        uint coveredLocation = (uint)(item.CurrentlyEquippedLocation & bodyLocationMask);
+        if (priority == 0 && coveredLocation is >= 0x200u and <= 0x4000u)
+            priority = 0x7Fu;
+        return priority;
+    }
+}