fix(ui): port source-aware toolbar drops

Plan retail shortcut drops from a complete post-lift snapshot so fresh inventory items use cyclic-right displacement while toolbar aliases restore to their vacated slot. Apply local mutations atomically, preserve raw shortcut fields, emit exact Remove/Add ordering, and retire AP-102 after the live ACE gate.

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

src/AcDream.Core/Items/ShortcutStore.cs

@@ -30,6 +30,9 @@ public sealed class ShortcutStore
     public ShortcutEntry? GetEntry(int slot)
         => (uint)slot < SlotCount ? _entries[slot] : null;
 
+    /// <summary>Detached raw snapshot for planning a complete mutation before applying it.</summary>
+    public ShortcutEntry?[] Snapshot() => (ShortcutEntry?[])_entries.Clone();
+
     /// <summary>Visible object id at <paramref name="slot"/>, or zero.</summary>
     public uint Get(int slot) => GetEntry(slot)?.ObjectId ?? 0u;