Refactor asset pipeline to use file paths, improve import

- Switched asset handler interfaces and implementations to use file paths instead of FileStreams for all operations.
- Refactored mesh asset structure and parsing, moved meshlet logic to MeshProcessor, and introduced hierarchical MeshNode types.
- Updated texture asset handling: switched to bits-per-channel, improved mipmap/cubemap generation, and SPMD HDRI support.
- Updated shader asset handlers to use file paths and split code compilation logic.
- Improved asset registry: added event debouncing, better path handling, and import time/hash tracking.
- Added source generator for IAssetSettings registration to support polymorphic JSON serialization.
- Updated dependencies and tests; various minor fixes and cleanups.

src/Runtime/Ghost.Generator/AssetHandlerRegistrationGenerator.cs

@@ -88,3 +88,73 @@ internal static partial class {registerTypeName}
         return null;
     }
 }
+
+[Generator]
+internal class IAssetSettingsRegistrationGenerator : IIncrementalGenerator
+{
+    public void Initialize(IncrementalGeneratorInitializationContext context)
+    {
+        var settingsCandidates = context.SyntaxProvider
+            .CreateSyntaxProvider(
+                predicate: (s, _) => s is ClassDeclarationSyntax,
+                transform: GetAssetSettingsSymbol)
+            .Where(symbol => symbol != null)
+            .Collect();
+        context.RegisterSourceOutput(settingsCandidates, GenerateRegistrationCode);
+    }
+
+    private void GenerateRegistrationCode(SourceProductionContext context, ImmutableArray<INamedTypeSymbol> array)
+    {
+        if (array.IsDefaultOrEmpty)
+        {
+            return;
+        }
+
+        var sb = new System.Text.StringBuilder();
+
+        foreach (var iface in array)
+        {
+            sb.AppendLine($"        global::Ghost.Editor.Core.AssetHandler.AssetHandlerRegistry.RegisterIAssetSettingsType(typeof({iface.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}), \"{iface.Name}\");");
+        }
+
+        var registerTypeName = "g_iassetsettings_registeration";
+        var code = $@"// <auto-generated />
+
+[global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+internal static partial class {registerTypeName}
+{{
+    [global::System.Runtime.CompilerServices.ModuleInitializer]
+    internal static void RegisterIAssetSettingsTypes()
+    {{
+{sb}
+    }}
+}}";
+
+        context.AddSource($"{registerTypeName}.gen.cs", code);
+    }
+
+    private INamedTypeSymbol GetAssetSettingsSymbol(GeneratorSyntaxContext context, CancellationToken token)
+    {
+        var classSyntax = (ClassDeclarationSyntax)context.Node;
+        if (context.SemanticModel.GetDeclaredSymbol(classSyntax) is not INamedTypeSymbol symbol)
+        {
+            return null;
+        }
+
+        var iSettingsSymbol = context.SemanticModel.Compilation.GetTypeByMetadataName("Ghost.Editor.Core.AssetHandler.IAssetSettings");
+        if (iSettingsSymbol == null)
+        {
+            return null;
+        }
+
+        foreach (var iface in symbol.AllInterfaces)
+        {
+            if (SymbolEqualityComparer.Default.Equals(iface, iSettingsSymbol))
+            {
+                return symbol;
+            }
+        }
+
+        return null;
+    }
+}