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/Rendering/TextRenderer.cs

@@ -201,6 +201,23 @@ public sealed class TextRenderer : IDisposable
         });
     }
 
+    /// <summary>
+    /// Campaign LA gate round 2 (register AD-98): uniform canvas scale applied
+    /// to every emitted quad — sprites, rects, AND glyphs — at the single
+    /// emission chokepoint (<see cref="AppendQuad"/>). Retail renders its
+    /// fixed-canvas pre-world screens (char select's authored 800×600, root
+    /// 0x1000039A, zero edge anchors) at authored size and stretches the whole
+    /// composed frame once at presentation; its UI blitter has no stretch mode
+    /// at all (Graphic::Draw @0x00693b20 is copy-or-tile only). We have no
+    /// present-time frame stretch, so the equivalent lives here: while a
+    /// fixed-canvas screen is active, <see cref="UiRoot"/> sets this for the
+    /// duration of its Draw and everything scales together — including retail's
+    /// characteristic non-uniform aspect distortion and stretched glyphs.
+    /// UVs and colors are untouched. Always reset to One outside UiRoot.Draw
+    /// so the world-space HUD keeps native pixels.
+    /// </summary>
+    internal Vector2 CanvasScale = Vector2.One;
+
     /// <summary>Begin a HUD pass. Call once per frame before any Draw* calls.</summary>
     public void Begin(Vector2 screenSize)
     {
@@ -388,10 +405,19 @@ public sealed class TextRenderer : IDisposable
         return ns;
     }
 
-    private static void AppendQuad(List<float> buf,
+    private void AppendQuad(List<float> buf,
         float x, float y, float w, float h,
         float u0, float v0, float u1, float v1, Vector4 color)
     {
+        // AD-98 canvas stretch — see CanvasScale's doc comment. Applied after
+        // all canvas-space clipping, so geometry and UVs stay consistent.
+        if (CanvasScale != Vector2.One)
+        {
+            x *= CanvasScale.X;
+            y *= CanvasScale.Y;
+            w *= CanvasScale.X;
+            h *= CanvasScale.Y;
+        }
         // Two triangles (6 verts). CCW in pixel space is clockwise in NDC
         // because the vertex shader flips Y, so OpenGL's default front-face
         // is GL_CCW — we rely on cull-face being disabled during HUD pass.