docs: update RHI API docs

docs/api/rhi/sampler/unbind.md

@@ -0,0 +1,52 @@
+# RHISampler::Unbind
+
+```cpp
+virtual void Unbind(unsigned int unit) = 0;
+```
+
+将采样器从指定的纹理单元解绑。该方法将指定的纹理单元上的采样器状态清除，使其不再占用该采样槽位。
+
+**参数：**
+
+| 参数 | 类型 | 描述 |
+|------|------|------|
+| `unit` | `unsigned int` | 纹理单元索引，指定从哪个纹理采样槽位解绑 |
+
+**返回：** 无
+
+**线程安全：** ❌
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include "XCEngine/RHI/RHISampler.h"
+
+class MySampler : public XCEngine::RHI::RHISampler {
+public:
+    void Shutdown() override { }
+    void Bind(unsigned int unit) override { m_boundUnit = unit; }
+    void Unbind(unsigned int unit) override {
+        if (m_boundUnit == unit) {
+            m_boundUnit = -1;
+        }
+    }
+    void* GetNativeHandle() override { return nullptr; }
+    unsigned int GetID() override { return 0; }
+
+private:
+    int m_boundUnit = -1;
+};
+
+void Example() {
+    MySampler sampler;
+    sampler.Bind(0);
+    sampler.Unbind(0);
+}
+```
+
+## 相关文档
+
+- [RHISampler 总览](sampler.md) - 返回类总览
+- [RHISampler::Bind](bind.md) - 绑定采样器