refactor(net): #13 rename Shortcut → ShortcutEntry, expand doc citations

Code review nit-fix on top of d3b58c9 — addresses two issues from the
quality review of Task 1:

  I1 (Important): the record struct `Shortcut` was a homograph with the
  flag member `CharacterOptionDataFlag.Shortcut`. Both names live inside
  `PlayerDescriptionParser`'s scope. Rename to `ShortcutEntry` aligns
  with `InventoryEntry`/`EquippedEntry` and removes the trap before
  Task 3's walker references both names in the same method body.

  M2 (Minor): `EquippedEntry` had no holtburger source citation; added
  one referencing events.rs:180-190. Also expanded `InventoryEntry`'s
  comment with the strict reader's validation reference.

Plan doc updated in lockstep so Task 3+ implementers see the new name.
8/8 PlayerDescriptionParser tests still pass.

src/AcDream.Core.Net/Messages/PlayerDescriptionParser.cs

@@ -198,20 +198,30 @@ public static class PlayerDescriptionParser
     }
 
     /// <summary>One shortcut bar entry. 16 bytes wire size.
-    /// holtburger shortcuts.rs:13-34.</summary>
+    /// holtburger <c>shortcuts.rs:13-34</c>. Named <c>ShortcutEntry</c>
-    public readonly record struct Shortcut(
+    /// (not <c>Shortcut</c>) to avoid a homograph with the
+    /// <see cref="CharacterOptionDataFlag.Shortcut"/> flag bit, which is
+    /// referenced from the same scope as instances of this type in the
+    /// trailer walker.</summary>
+    public readonly record struct ShortcutEntry(
         uint Index,
         uint ObjectGuid,
         ushort SpellId,
         ushort Layer);
 
-    /// <summary>One inventory entry — a guid plus a ContainerType discriminator
+    /// <summary>One inventory entry — a guid plus a ContainerType
-    /// (0=NonContainer, 1=Container, 2=Foci).</summary>
+    /// discriminator (0=NonContainer, 1=Container, 2=Foci). Holtburger
+    /// <c>events.rs:143-168</c> validates <c>ContainerType &lt;= 2</c>
+    /// in <c>unpack_inventory_and_equipped_strict</c>.</summary>
     public readonly record struct InventoryEntry(
         uint Guid,
         uint ContainerType);
 
-    /// <summary>One equipped object entry.</summary>
+    /// <summary>One equipped object entry. Holtburger
+    /// <c>events.rs:180-190</c>: <c>(Guid guid, u32 loc, u32 prio)</c>.
+    /// <paramref name="EquipLocation"/> is an <c>EquipMask</c> bitfield;
+    /// <paramref name="Priority"/> orders overlapping equips in the
+    /// same slot.</summary>
     public readonly record struct EquippedEntry(
         uint Guid,
         uint EquipLocation,
@@ -231,7 +241,7 @@ public static class PlayerDescriptionParser
         CharacterOptionDataFlag OptionFlags,
         uint Options1,
         uint Options2,
-        IReadOnlyList<Shortcut> Shortcuts,
+        IReadOnlyList<ShortcutEntry> Shortcuts,
         IReadOnlyList<IReadOnlyList<uint>> HotbarSpells,
         IReadOnlyList<(uint Id, uint Amount)> DesiredComps,
         uint SpellbookFilters,
@@ -312,7 +322,7 @@ public static class PlayerDescriptionParser
                 weenieType, propertyFlags, vectorFlags, hasHealth,
                 bundle, positions, attributes, skills, spells, enchantments,
                 CharacterOptionDataFlag.None, 0u, 0u,
-                System.Array.Empty<Shortcut>(),
+                System.Array.Empty<ShortcutEntry>(),
                 System.Array.Empty<IReadOnlyList<uint>>(),
                 System.Array.Empty<(uint, uint)>(),
                 0u,
@@ -341,7 +351,7 @@ public static class PlayerDescriptionParser
             bundle, positions, attributes, skills, spells,
             System.Array.Empty<EnchantmentEntry>(),
             CharacterOptionDataFlag.None, 0u, 0u,
-            System.Array.Empty<Shortcut>(),
+            System.Array.Empty<ShortcutEntry>(),
             System.Array.Empty<IReadOnlyList<uint>>(),
             System.Array.Empty<(uint, uint)>(),
             0u,