前端：增加BGM提示词助手状态与客户端

增加补全与简化内部客户端及共享DTO
实现对话框级状态、取消、迟到响应保护和交换式撤销
接入画布生成工作流并将submitting设为排他锁
补齐同步读取、项目切换和字符边界回归测试

packages/shared/src/contracts/editorAudio.ts

@@ -0,0 +1,8 @@
+export type BackgroundMusicPromptAssistRequest = {
+  currentPrompt: string;
+};
+
+export type BackgroundMusicPromptAssistResponse = {
+  prompt: string;
+  charCount: number;
+};

packages/shared/src/contracts/index.ts

@@ -2,6 +2,7 @@ export type * from './barkBattle';
 export type * from './creationAudio';
 export type * from './creativeAgent';
 export * from './editorAgent';
+export type * from './editorAudio';
 export * from './gameCreationApp';
 export * from './hostBridge';
 export type * from './hyper3d';

packages/shared/src/index.ts

@@ -5,6 +5,7 @@ export type * from './contracts/creationAgentDocumentInput';
 export type * from './contracts/creationAudio';
 export type * from './contracts/creativeAgent';
 export type * from './contracts/customWorldAgent';
+export type * from './contracts/editorAudio';
 export * from './contracts/edutainmentBabyDrawing';
 export * from './contracts/edutainmentBabyObject';
 export * from './contracts/externalGeneration';