Refactor pipeline state and render output abstractions

- Replace old pipeline enums/structs with new strongly-typed PipelineState and enums (ZTest, ZWrite, Cull, Blend, ColorWriteMask)
- Redesign pipeline keying: introduce 128-bit GraphicsPipelineKey, MaterialPipelineKey, and PassPipelineKey for robust PSO caching
- Replace IRenderTargetStrategy with IRenderOutput; add SwapChainRenderOutput and TextureRenderOutput
- Update renderer and window code to use new render output abstraction and handle viewport/scissor updates
- Make ShaderPass a readonly struct and Shader a struct; use ID-based pass lookup for efficiency
- Materials now support per-pass pipeline overrides with new keying
- Add defensive checks in D3D12CommandBuffer; update D3D12PipelineLibrary for new keying/state
- Move test shader to test.gsdef and update for new pipeline state syntax
- Remove obsolete files/interfaces and perform general code cleanups
- Update all usages and parsing logic for new pipeline state system

Ghost.Graphics/Contracts/IRenderOutput.cs

@@ -0,0 +1,43 @@
+using Ghost.Core;
+using Ghost.Graphics.Core;
+using Ghost.Graphics.RHI;
+
+namespace Ghost.Graphics.Contracts;
+
+public interface IRenderOutput
+{
+    ViewportDesc Viewport
+    {
+        get; set;
+    }
+
+    RectDesc Scissor
+    {
+        get; set;
+    }
+
+    /// <summary>
+    /// Gets a handle to the current render target texture.
+    /// </summary>
+    /// <returns>A handle to the texture that is currently set as the render target.</returns>
+    Handle<Texture> GetRenderTarget();
+
+    /// <summary>
+    /// Begins a rendering operation using the specified command buffer. Typically this will include resource barriers,
+    /// </summary>
+    /// <param name="cmd">The command buffer that records rendering commands.</param>
+    /// 
+    void BeginRender(ICommandBuffer cmd);
+    /// <summary>
+    /// Finalizes the rendering process using the specified command buffer.
+    /// </summary>
+    /// <param name="cmd">The command buffer that contains the rendering commands to be finalized.</param>
+    void EndRender(ICommandBuffer cmd);
+
+    /// <summary>
+    /// Displays the current frame to the output device or screen.
+    /// </summary>
+    /// <remarks>Call this method after rendering operations to present the rendered content. The exact
+    /// behavior may depend on the underlying graphics implementation or device.</remarks>
+    void Present();
+}