GhostEngine Render Graph: major refactor & Unity RG ref

- Major architectural refactor for performance, extensibility, and feature completeness: resource pooling, pass culling, aliasing, and compilation caching.
- Introduces type-safe builder and context APIs, blackboard pattern, and unified resource management.
- Adds detailed documentation and cleans up obsolete files and APIs.
- Includes (commented) Unity Render Graph source for reference; not compiled, for parity and future extension.

Ghost.RenderGraph.Concept/PassData.cs

@@ -1,14 +1,16 @@
 namespace Ghost.RenderGraph.Concept;
 
-// Pass data structure for GBuffer outputs
-public class GBufferData
+// ===== Pass Data Structures =====
+// These are user-defined data structures that get passed to render functions
+
+public sealed class GBufferData : IPassData
 {
     public RenderGraphTextureHandle Albedo;
     public RenderGraphTextureHandle Normal;
     public RenderGraphTextureHandle Depth;
 }
 
-public class LightingPassData
+public sealed class LightingPassData : IPassData
 {
     public RenderGraphTextureHandle GBufferAlbedo;
     public RenderGraphTextureHandle GBufferNormal;
@@ -16,43 +18,38 @@ public class LightingPassData
     public RenderGraphTextureHandle OutputLighting;
 }
 
-public class SSAOPassData
+public sealed class SSAOPassData : IPassData
 {
     public RenderGraphTextureHandle GBufferDepth;
     public RenderGraphTextureHandle GBufferNormal;
     public RenderGraphTextureHandle OutputSSAO;
 }
 
-public class TAAPassData
-{
-    public RenderGraphTextureHandle InputLighting;
-    public RenderGraphTextureHandle OutputTAA;
-}
-
-public class PostProcessingPassData
-{
-    public RenderGraphTextureHandle InputTAA;
-    public RenderGraphTextureHandle InputSSAO;
-    public RenderGraphTextureHandle OutputBackbuffer;
-}
-
-public class DebugPassData
-{
-    public RenderGraphTextureHandle DebugTexture;
-}
-
-public class ProfilerMarkerData { }
-
-public class BloomDownsampleData
+public sealed class BloomDownsampleData : IPassData
 {
     public RenderGraphTextureHandle Input;
     public RenderGraphTextureHandle Output;
 }
 
-public class PostProcessingPassDataV2
+public sealed class TAAPassData : IPassData
+{
+    public RenderGraphTextureHandle InputLighting;
+    public RenderGraphTextureHandle OutputTAA;
+}
+
+public sealed class PostProcessingPassDataV2 : IPassData
 {
     public RenderGraphTextureHandle InputTAA;
     public RenderGraphTextureHandle InputSSAO;
     public RenderGraphTextureHandle InputBloom;
     public RenderGraphTextureHandle OutputBackbuffer;
 }
+
+public sealed class ProfilerMarkerData : IPassData
+{
+}
+
+public sealed class DebugPassData : IPassData
+{
+    public RenderGraphTextureHandle DebugTexture;
+}