Add BuildFontsAsync for parallel font/theme init

HellionChat/FontManager.cs

@@ -100,6 +100,19 @@ public class FontManager
         JpRange = BuildRange(GlyphRangesJapanese.GlyphRanges);
     }
 
+    /// <summary>
+    /// Async wrapper around <see cref="BuildFonts"/> for the Phase-1 LoadAsync
+    /// path. The font-atlas build is CPU-bound, so we offload via Task.Run and
+    /// honour the cancellation token at the scheduling boundary; this lets the
+    /// font build run in parallel with the theme init without blocking the
+    /// loader. Settings-driven manual rebuilds keep using the sync entry point.
+    /// </summary>
+    public async Task BuildFontsAsync(CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        await Task.Run(BuildFonts, cancellationToken).ConfigureAwait(false);
+    }
+
     public void BuildFonts()
     {
         SetUpRanges();

HellionChat/Plugin.cs

@@ -490,11 +490,10 @@ public sealed class Plugin : IAsyncDalamudPlugin
             // Group A: Font + Theme parallel — both CPU-bound, independent, and
             // dominate the load-time profile. Everything else stays sequential to
             // keep ordering simple.
-            var fontTask = Task.Run(() =>
+            var fontTask = Task.Run(async () =>
             {
                 FontManager = new FontManager();
-                // TODO(v1.4.x): replace with FontManager.BuildFontsAsync(cancellationToken)
-                FontManager.BuildFonts();
+                await FontManager.BuildFontsAsync(cancellationToken).ConfigureAwait(false);
             }, cancellationToken);
 
             var themeTask = Task.Run(() =>