Refactor render graph: modular compilation & execution

Major overhaul of render graph system for modularity and performance:
- Split compilation and execution logic into dedicated classes (Compiler, Executor, NativePassBuilder, Barriers)
- Overhauled barrier system: now uses CompiledBarrier with target state only, querying before state at execution
- Resource size/alignment now queried from D3D12 device for accurate heap allocation
- ResourceDesc now includes Type field and asserts correct union access
- Centralized D3D12 interop logic in D3D12Utility extensions
- Added RenderGraphHasher for structural graph hashing and cache invalidation
- RenderGraph class simplified to orchestrate specialized components
- ResourceAliasingManager now uses allocator for size queries
- Compilation cache now stores compiled barriers, reducing memory usage
- Improved comments, debug assertions, and removed redundant code

Result: more maintainable, efficient, and robust render graph pipeline.

Ghost.Graphics/RenderGraphModule/RenderGraphCompilationCache.cs

@@ -23,11 +23,8 @@ internal sealed class CachedCompilation
     // Placed resource metadata
     public readonly List<PlacedResourceData> placedResources = new(32);
     
-    // Resource barriers
-    public readonly List<ResourceBarrier> barriers = new(128);
-    
-    // Resource state mappings (for barrier generation)
-    public readonly Dictionary<int, ResourceBarrierData> resourceStates = new(128);
+    // Compiled barriers (stores only target states, queries before state from ResourceDatabase)
+    public readonly List<CompiledBarrier> compiledBarriers = new(128);
 
     // Real gpu resource
     public readonly List<Handle<GPUResource>> backingResources = new(32);
@@ -41,8 +38,7 @@ internal sealed class CachedCompilation
         passCulledFlags.Clear();
         logicalToPhysical.Clear();
         placedResources.Clear();
-        barriers.Clear();
-        resourceStates.Clear();
+        compiledBarriers.Clear();
         backingResources.Clear();
         viewState = default;
     }
@@ -112,12 +108,7 @@ internal sealed class RenderGraphCompilationCache
         }
         
         _cached.placedResources.AddRange(data.placedResources);
-        _cached.barriers.AddRange(data.barriers);
-        
-        foreach (var kvp in data.resourceStates)
-        {
-            _cached.resourceStates[kvp.Key] = kvp.Value;
-        }
+        _cached.compiledBarriers.AddRange(data.compiledBarriers);
 
         _cached.backingResources.AddRange(data.backingResources);
     }