fix(core): 导出命令系统函数供 Server 使用

packages/core/src/index.ts

@@ -32,6 +32,10 @@ export { loadConfig } from './utils/config.js';
 export { SessionStorage } from './session/storage.js';
 export type { SessionData, SessionSummary } from './session/types.js';
 
+// Commands
+export { getCommandRegistry, createCommandExecutor } from './commands/index.js';
+export type { Command, CommandInput, CommandExecutionResult } from './commands/index.js';
+
 const program = new Command();
 
 // MCP 管理器实例