feat(D.2b): UiField (Type 3) — editable input as a generic field; remove the stray Type-12 input placeholder (widget-generalization Task 6)

- Rename UiChatInput → UiField (UIElement_Field, RegisterElementClass(3) @ :126190);
  update doc to cite retail's CatchDroppedItem/MouseOverTop drag-drop hooks for
  future item windows. BackgroundColor default → transparent (controller sets
  the translucent 0.35α value explicitly, matching UiText pattern).
- Register Type 3 in DatWidgetFactory.Create: `3 => new UiField()`.
- ChatWindowController.Bind (Variant B): factory now builds 0x10000016 as an
  invisible UiText placeholder (Type 12); Bind removes that placeholder via
  FindElement(InputId).Parent.RemoveChild and places a UiField at the same rect.
  Result: exactly ONE input widget in the input bar, no stray UiText duplicate.
- Input property type changed from UiChatInput to UiField; GameWindow.cs:1861
  UiField.Keyboard assignment compiles unchanged (field exists).
- Tests: UiChatInputTests → UiFieldTests (class + all ctor refs renamed);
  DatWidgetFactoryTests: new Type3_Field_MakesUiField test; ChatWindowControllerTests:
  updated stale "skipped by factory" comments; LayoutConformanceTests: updated
  VitalsTree_ChromeCornerHasExpectedSprite — Type-3 chrome-corner elements are
  now UiField (sprite rendering for Type-3 dat image elements is a known
  limitation, tracked for post-Task-8 UiField.BackgroundSprite follow-up).
- Full suite: 404 passed, 2 skipped, 0 failed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/UI/Layout/ChatWindowController.cs

@@ -14,15 +14,14 @@ namespace AcDream.App.UI.Layout;
 /// analogue of retail <c>ChatInterface</c> + <c>gmMainChatUI::PostInit @0x4ce130</c>.
 ///
 /// <para>
-/// The transcript (<c>0x10000011</c>) and input (<c>0x10000016</c>) are Type-0
-/// elements whose base is a Type-12 prototype, so the importer factory skips them
-/// (returns null). This controller reads their rects from the raw
-/// <see cref="ElementInfo"/> tree (which contains everything) and adds the behavioral
-/// widgets as children of their parent container widgets (transcript panel
-/// <c>0x10000010</c> / input bar <c>0x10000013</c>) which ARE created as
-/// <see cref="UiDatElement"/> nodes. The scrollbar track (<c>0x10000012</c>) is built
-/// directly as a <see cref="UiScrollbar"/> by the factory (Type 11) and is bound in place
-/// here. The channel menu (<c>0x10000014</c>) is still replaced with its behavioral counterpart.
+/// The transcript (<c>0x10000011</c>) is Type-12 and is built as a <see cref="UiText"/>
+/// by the factory; this controller binds its live data provider in place. The input
+/// (<c>0x10000016</c>) is also Type-12, so the factory builds it as an invisible
+/// <see cref="UiText"/> placeholder; this controller removes that placeholder and adds
+/// a <see cref="UiField"/> at the same rect. The scrollbar track (<c>0x10000012</c>) is
+/// built directly as a <see cref="UiScrollbar"/> by the factory (Type 11) and bound in
+/// place. The channel menu (<c>0x10000014</c>) is built as <see cref="UiMenu"/> (Type 6)
+/// and bound in place.
 /// </para>
 /// </summary>
 public sealed class ChatWindowController
@@ -37,7 +36,7 @@ public sealed class ChatWindowController
     private const uint TrackId        = 0x10000012u;
     private const uint InputBarId     = 0x10000013u;
     private const uint MenuId         = 0x10000014u;
-    private const uint InputId        = 0x10000016u;   // Type-12 prototype — skipped by factory
+    private const uint InputId        = 0x10000016u;   // Type-12 Text — factory builds UiText placeholder; Bind removes + replaces with UiField
     private const uint SendId         = 0x10000019u;
     private const uint MaxMinId       = 0x1000046Fu;
 
@@ -68,7 +67,7 @@ public sealed class ChatWindowController
     public UiText Transcript { get; private set; } = null!;
 
     /// <summary>Editable chat input widget. Null until <see cref="Bind"/> succeeds.</summary>
-    public UiChatInput Input { get; private set; } = null!;
+    public UiField Input { get; private set; } = null!;
 
     /// <summary>Scrollbar widget, driven by <see cref="Transcript"/>'s scroll model.</summary>
     public UiScrollbar Scrollbar { get; private set; } = null!;
@@ -160,9 +159,9 @@ public sealed class ChatWindowController
         BitmapFont? debugFont,
         Func<uint, (uint tex, int w, int h)> resolve)
     {
-        // The transcript is now built as a UiText by the factory (Type 12 is no longer skipped).
-        // The input node (0x10000016) is still Type-12 based; find it in the raw ElementInfo
-        // tree to read its rect for the behavioral UiChatInput widget.
+        // The transcript is built as a UiText by the factory (Type 12).
+        // The input node (0x10000016) is also Type-12 → UiText, but the controller replaces
+        // it with a UiField. Read its rect from the raw ElementInfo tree first.
         var iInfo = FindInfo(rootInfo, InputId);
 
         // Their parent panels must exist as real widgets in the layout tree.
@@ -214,8 +213,12 @@ public sealed class ChatWindowController
         c.Transcript.LinesProvider   = () => BuildLines(vm, c.Transcript, datFont, debugFont);
 
         // ── Input ────────────────────────────────────────────────────────
-        // Place the behavioral input widget inside the input bar.
-        c.Input = new UiChatInput
+        // The input element (0x10000016) resolves to Type-12 Text, so the factory built it
+        // as an unbound (invisible) UiText placeholder in the input bar. The editable entry
+        // is a controller-placed UiField at the same rect — drop the placeholder, add the field.
+        if (layout.FindElement(InputId) is { Parent: { } inParent } inputPlaceholder)
+            inParent.RemoveChild(inputPlaceholder);
+        c.Input = new UiField
         {
             Left    = iInfo.X,
             Top     = iInfo.Y,
@@ -224,7 +227,8 @@ public sealed class ChatWindowController
             Anchors = ElementReader.ToAnchors(iInfo.Left, iInfo.Top, iInfo.Right, iInfo.Bottom),
             DatFont = datFont,
             Font    = debugFont,
-            SpriteResolve   = resolve,
+            BackgroundColor = new Vector4(0f, 0f, 0f, 0.35f),   // retail translucent unfocused field
+            SpriteResolve    = resolve,
             FocusFieldSprite = InputFocusField,
         };
         inputBar.AddChild(c.Input);

src/AcDream.App/UI/Layout/DatWidgetFactory.cs

@@ -52,6 +52,7 @@ public static class DatWidgetFactory
         UiElement e = info.Type switch
         {
             1  => new UiButton(info, resolve),         // UIElement_Button (reg :125828)
+            3  => new UiField(),                       // UIElement_Field (reg :126190)
             6  => new UiMenu(),                        // UIElement_Menu (reg :120163)
             7  => BuildMeter(info, resolve, datFont),  // UIElement_Meter
             11 => new UiScrollbar(),                   // UIElement_Scrollbar (reg :124137)