perf(runtime): remove measured steady allocations

Eliminate boxed production surface-override enumeration, retain vital modifier projections until the enchantment registry mutates, and measure DAT font widths without allocating a captured delegate. Preserve exact hashes, spell stacking, and glyph advances with warmed zero-allocation tests.

Validated by the focused rendering, UI, and spell suites, a zero-error Release build, and 8,409 passing Release tests with five pre-existing skips.

Co-authored-by: Codex <codex@openai.com>

src/AcDream.App/Rendering/Scene/CurrentRenderSceneOracle.cs

@@ -848,18 +848,33 @@ internal sealed class CurrentRenderSceneOracle :
         ulong xorHigh = 0;
         ulong sumLow = 0;
         ulong sumHigh = 0;
-        foreach ((uint surfaceId, uint replacementId) in overrides)
+        if (overrides is Dictionary<uint, uint> dictionary)
         {
-            StableRenderHash128 pair = StableRenderHash128.Create();
-            pair.Add(surfaceId);
-            pair.Add(replacementId);
-            RenderSceneHash128 value = pair.Finish();
-            xorLow ^= value.Low;
-            xorHigh ^= value.High;
-            unchecked
+            // Production hydration owns Dictionary instances. Enumerating
+            // through IReadOnlyDictionary boxes Dictionary.Enumerator for
+            // every live mesh on both projection-sync phases.
+            foreach (KeyValuePair<uint, uint> pair in dictionary)
             {
-                sumLow += value.Low;
-                sumHigh += value.High;
+                Accumulate(
+                    pair.Key,
+                    pair.Value,
+                    ref xorLow,
+                    ref xorHigh,
+                    ref sumLow,
+                    ref sumHigh);
+            }
+        }
+        else
+        {
+            foreach ((uint surfaceId, uint replacementId) in overrides)
+            {
+                Accumulate(
+                    surfaceId,
+                    replacementId,
+                    ref xorLow,
+                    ref xorHigh,
+                    ref sumLow,
+                    ref sumHigh);
             }
         }
 
@@ -870,6 +885,27 @@ internal sealed class CurrentRenderSceneOracle :
         geometry.Add(sumLow);
         geometry.Add(sumHigh);
         return geometry.Finish();
+
+        static void Accumulate(
+            uint surfaceId,
+            uint replacementId,
+            ref ulong xorLow,
+            ref ulong xorHigh,
+            ref ulong sumLow,
+            ref ulong sumHigh)
+        {
+            StableRenderHash128 pairHash = StableRenderHash128.Create();
+            pairHash.Add(surfaceId);
+            pairHash.Add(replacementId);
+            RenderSceneHash128 value = pairHash.Finish();
+            xorLow ^= value.Low;
+            xorHigh ^= value.High;
+            unchecked
+            {
+                sumLow += value.Low;
+                sumHigh += value.High;
+            }
+        }
     }
 
     internal static RenderSceneHash128 FingerprintSelectionGeometry(

src/AcDream.App/UI/UiDatFont.cs

@@ -62,7 +62,7 @@ public sealed class UiDatFont
 
     private readonly Dictionary<char, FontCharDesc> _glyphs;
 
-    private UiDatFont(
+    internal UiDatFont(
         uint fgTex, int fgW, int fgH,
         uint bgTex, int bgW, int bgH,
         float lineHeight, float baselineOffset,
@@ -131,7 +131,18 @@ public sealed class UiDatFont
     /// glyph's retail advance. Characters not in the font contribute nothing.
     /// </summary>
     public float MeasureWidth(string text)
-        => MeasureWidth(text, c => _glyphs.TryGetValue(c, out var g) ? g : null);
+    {
+        if (string.IsNullOrEmpty(text)) return 0f;
+
+        float width = 0f;
+        for (int index = 0; index < text.Length; index++)
+        {
+            if (_glyphs.TryGetValue(text[index], out FontCharDesc? glyph))
+                width += GlyphAdvance(glyph);
+        }
+
+        return width;
+    }
 
     /// <summary>
     /// Pure pen-advance summation seam: total width of <paramref name="text"/>