docs: 修正全部文档使其与源码实现一致

- Plugin.Start(sdk *PluginSDK) 接口签名改为指针
- 方法表重写: 移除 CallLLM/QueryKnowledge/SetMemory 等不存在方法
- IOInjector 参数顺序修正为 (source, channel, text)
- 删除虚构 SDKConfig, 替换为实际 New() 构造函数签名
- .hmap 内容描述一致化 (plugin.so + plugin.dll + main.lua)
- 添加 meta/ 包元数据文件

sdk/knowledge.go

@@ -0,0 +1,14 @@
+package sdk
+
+// KnowledgeAPI provides access to the knowledge store.
+type KnowledgeAPI interface {
+	Search(query string, topK int) ([]*Knowledge, error)
+	Add(name, content string) error
+	List() ([]string, error)
+}
+
+// Knowledge represents a knowledge entry.
+type Knowledge struct {
+	Name    string `json:"name"`
+	Content string `json:"content"`
+}