feat(ui): importer Fix C — per-element dat FontDid resolver (studio path); character level uses its retail font

DatWidgetFactory.Create now accepts an optional fontResolve: Func<uint,UiDatFont?>
parameter. When supplied and the element has a non-zero FontDid, the element
receives its own dat font instead of the shared global datFont fallback.
Null = original single-font behavior (the live GameWindow path passes null —
provably unchanged). LayoutImporter.Build/BuildFromInfos/Import all thread
the optional resolver down to the factory.

RenderStack gains a lazy font cache (ConcurrentDictionary, pre-seeded with
VitalsDatFont + LargeDatFont) and a ResolveDatFont(uint) method. StudioWindow
wires stack.ResolveDatFont into LayoutSource so every studio import gets
per-element fonts. GameWindow import calls left passing null (follow-up todo).

CharacterStatController font-hack cleanup (diagnosed via one-shot console dump
then removed):
- Name (0x10000231): dat FontDid = 18px font — remove datFont override (null)
- Heritage/PkStatus: dat FontDid = 14px fonts — remove override
- LevelCaption: dat FontDid = 16px — remove override (same font, no visual change)
- Level (0x1000023B): dat FontDid = 36px (the big retail gold font) — was forced
  to rowDatFont/LargeDatFont (18px); now drops to null so the dat 36px font drives
- TotalXpLabel/TotalXp: dat FontDid = 16px — remove override
- FooterTitle (0x1000024E): dat FontDid = 20px — remove datFont override
- KEEP: synthesized elements (XP meter overlays, 9 attribute rows, tab sprites)
  still use datFont directly since they have no dat origin

All Label/LabelTwoLine/LabelLeft/LabelProvider helpers updated: null = keep
build-time dat font; non-null = controller explicit override (backward-compat).

8 new tests in DatWidgetFactoryFontResolveTests:
- null resolver → DatFont == global datFont
- FontDid=0 → resolver not called
- resolver returns null → fallback to global datFont
- resolver called with element's FontDid
- controller DatFont override wins after build
- LayoutImporter.Build threads fontResolve to factory
- meter element fires resolver for non-zero FontDid
- BuildFromInfos without fontResolve param = original behavior

Build + all 710 App tests green.

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

src/AcDream.App/Rendering/RenderBootstrap.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using DatReaderWriter;
 using Microsoft.Extensions.Logging.Abstractions;
 using Silk.NET.OpenGL;
@@ -48,6 +49,46 @@ public sealed record RenderStack(
         uint t = TextureCache.GetOrUploadRenderSurface(spriteId, out int w, out int h);
         return (t, w, h);
     }
+
+    // ── Font cache (per-stack, keyed by FontDid) ─────────────────────────────
+
+    /// <summary>
+    /// Cache of loaded dat fonts keyed by FontDid (0x40000000-range).
+    /// Populated lazily by <see cref="ResolveDatFont"/>. Thread-safe for
+    /// concurrent reads from the studio render loop; writes happen only
+    /// during the first load of each distinct FontDid.
+    /// </summary>
+    private readonly ConcurrentDictionary<uint, AcDream.App.UI.UiDatFont?> _fontCache = new();
+
+    /// <summary>
+    /// Lazily load and cache a dat font by its FontDid. Returns null (and
+    /// caches null) when the Font DBObj is absent or has no foreground surface —
+    /// callers fall back to the global font in that case.
+    ///
+    /// <para>Pre-seeds <see cref="VitalsDatFont"/> (0x40000000) and
+    /// <see cref="LargeDatFont"/> (0x40000001) from the already-loaded instances
+    /// to avoid a redundant upload on those two ids.</para>
+    /// </summary>
+    public AcDream.App.UI.UiDatFont? ResolveDatFont(uint fontDid)
+    {
+        return _fontCache.GetOrAdd(fontDid, id =>
+            AcDream.App.UI.UiDatFont.Load(Dats, TextureCache, id));
+    }
+
+    /// <summary>
+    /// Pre-seeds the font cache from the two already-loaded font instances
+    /// (VitalsDatFont = 0x40000000, LargeDatFont = 0x40000001) so that
+    /// <see cref="ResolveDatFont"/> returns them without a redundant GL upload.
+    /// Called once by <see cref="RenderBootstrap.Create"/> after the stack is
+    /// fully constructed.
+    /// </summary>
+    internal void SeedFontCache()
+    {
+        if (VitalsDatFont is not null)
+            _fontCache.TryAdd(AcDream.App.UI.UiDatFont.DefaultFontId, VitalsDatFont);
+        if (LargeDatFont is not null)
+            _fontCache.TryAdd(0x40000001u, LargeDatFont);
+    }
 }
 
 /// <summary>Options for <see cref="RenderBootstrap.Create"/>.</summary>
@@ -159,7 +200,7 @@ public static class RenderBootstrap
         //     UI Studio, and BitmapFont requires a system font byte array) ---
         var uiHost = new AcDream.App.UI.UiHost(gl, shaderDir, defaultFont: null);
 
-        return new RenderStack(
+        var stack = new RenderStack(
             Gl:                  gl,
             Dats:                dats,
             ShaderDir:           shaderDir,
@@ -173,6 +214,13 @@ public static class RenderBootstrap
             UiHost:              uiHost,
             VitalsDatFont:       vitalsDatFont,
             LargeDatFont:        largeDatFont);
+
+        // Pre-seed the font cache with the two already-uploaded atlas instances
+        // so ResolveDatFont(0x40000000) and ResolveDatFont(0x40000001) hit the cache
+        // rather than re-uploading the same GL texture a second time.
+        stack.SeedFontCache();
+
+        return stack;
     }
 
     // NullAnimLoader mirrors GameWindow's private NullAnimLoader (GameWindow ~13327-13330).