docs: update RHI API docs

docs/api/rhi/command-list/set-blend-state.md

@@ -4,10 +4,18 @@
 virtual void SetBlendState(const BlendState& state) = 0;
 ```
 
-设置混合状态。
+设置颜色混合状态。控制源颜色和目标颜色如何混合，影响最终输出像素的颜色值。
 
 **参数：**
-- `state` - 混合状态结构体
+- `state` - 混合状态结构体（包含 alphaToCoverageEnable、independentBlendEnable、renderTargets[] 等）
+
+**返回：** `void`
+
+**异常：** 无
+
+**线程安全：** ❌
+
+**复杂度：** O(1)
 
 **示例：**
 
@@ -15,9 +23,15 @@ virtual void SetBlendState(const BlendState& state) = 0;
 BlendState blendState;
 blendState.alphaToCoverageEnable = false;
 blendState.independentBlendEnable = false;
+blendState.renderTargets[0].blendEnable = true;
+blendState.renderTargets[0].srcBlend = BlendFactor::SrcAlpha;
+blendState.renderTargets[0].dstBlend = BlendFactor::InvSrcAlpha;
+blendState.renderTargets[0].blendOp = BlendOp::Add;
 cmdList->SetBlendState(blendState);
 ```
 
 ## 相关文档
 
 - [RHICommandList 总览](command-list.md) - 返回类总览
+- [SetBlendFactor](set-blend-factor.md) - 设置混合因子
+- [SetPipelineState](set-pipeline-state.md) - 设置管线状态