fix(ui): Campaign LA gate round 2 — character-select scales as one authored canvas

Third iteration on the screen, completing AD-98. The previous substitution
stretched only the root BACKGROUND while the child widgets stayed at their
authored 800x600 pixel positions - and the background painting carries
visual anchors (the World/Characters captions are art), so the user gate
showed captions overlapping the listbox and every widget misaligned
against the stretched art.

Retail model (established at 71bf24fb): fixed-canvas pre-world screens
render at authored 800x600 and the whole composed frame stretches once at
presentation; the blitter has no stretch mode. Our equivalent now does the
same one stage earlier:

- UiRoot.FixedCanvasSize: while the char-select screen is active, the
  retained tree lays out in its authored canvas and Draw scopes a uniform
  scale onto TextRenderer.CanvasScale; the mouse entry points apply the
  exact inverse so MouseX/MouseY and every hit test live in canvas space.
- TextRenderer.AppendQuad is the single emission chokepoint - sprites,
  rects, AND glyphs scale together, including retail-authentic non-uniform
  aspect distortion and stretched text. World-space HUD stays native (the
  scale resets outside UiRoot.Draw).
- CharacterManagementUiController stops resizing Root to the viewport;
  activate/deactivate/dispose set and clear the host canvas.
- UiDatElement returns to retail-pure copy-or-tile; the interim
  StretchOwnBackgroundToFill flag is deleted.
- AD-98 updated to describe the completed substitution.

Tests: canvas-scale quad math, inverse input mapping (window click lands
on the canvas-space widget), degenerate-size guards, controller keeps
authored extent + sets/clears the canvas. App suite 5085/6 skips; live-DAT
char-select probes 3/3.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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

@@ -38,6 +38,7 @@ internal sealed class CharacterManagementUiController : IDisposable
     private readonly List<UiButton> _rows = [];
     private readonly Dictionary<UiButton, uint> _rowIds = [];
 
+    private Vector2 _authoredCanvas;
     private RuntimeGenerationToken _lastGeneration;
     private long _lastRevision = long.MinValue;
     private uint _deleteDialogContext;
@@ -74,24 +75,22 @@ internal sealed class CharacterManagementUiController : IDisposable
 
         Root.Left = 0f;
         Root.Top = 0f;
-        Root.Anchors = AnchorEdges.Left | AnchorEdges.Top
-            | AnchorEdges.Right | AnchorEdges.Bottom;
-        if (host.Width > 0f)
-            Root.Width = host.Width;
-        if (host.Height > 0f)
-            Root.Height = host.Height;
         Root.ClickThrough = false;
         Root.Visible = false;
 
-        // Campaign LA gate round 2: this root is resized to the live viewport just
-        // above, which is bigger than its authored 800x600 canvas at almost every
-        // real resolution. Its own DirectState background (RenderSurface 0x06007576)
-        // must scale to fill that resized rect, not tile — see
-        // UiDatElement.StretchOwnBackgroundToFill's doc comment for the retail
-        // mechanism (a fixed-canvas screen stretched once at presentation) this
-        // substitutes.
-        if (Root is UiDatElement rootBackground)
-            rootBackground.StretchOwnBackgroundToFill = true;
+        // Campaign LA gate round 2 (register AD-98): the root KEEPS its authored
+        // 800×600 extent — retail never resizes it (zero edge anchors, verified
+        // against the installed DAT) and its blitter has no stretch mode; the
+        // whole composed screen stretches once at presentation. Our equivalent:
+        // while this screen is active, the host stretches the ENTIRE canvas —
+        // widgets, glyphs, and the painted background (which carries the
+        // "World"/"Characters" captions as art) — as one unit via
+        // UiRoot.FixedCanvasSize. Resizing the root here instead is exactly the
+        // half-substitution that misaligned the widgets against the stretched
+        // art at the 2026-08-15 user gate.
+        _authoredCanvas = new Vector2(
+            Root.Width > 0f ? Root.Width : 800f,
+            Root.Height > 0f ? Root.Height : 600f);
 
         // Create Character belongs to a future campaign. Keep retail's
         // authored control in place and visibly ghosted; do not hide it or
@@ -246,6 +245,7 @@ internal sealed class CharacterManagementUiController : IDisposable
         {
             _active = true;
             Root.Visible = true;
+            _host.FixedCanvasSize = _authoredCanvas;
             _host.BringToFront(Root);
         }
 
@@ -310,6 +310,7 @@ internal sealed class CharacterManagementUiController : IDisposable
         }
         finally
         {
+            _host.FixedCanvasSize = null;
             _enter.OnClick = null;
             _delete.OnClick = null;
             _restore.OnClick = null;
@@ -665,6 +666,7 @@ internal sealed class CharacterManagementUiController : IDisposable
         {
             _active = false;
             Root.Visible = false;
+            _host.FixedCanvasSize = null;
         }
         foreach (UiButton row in _rows)
         {