feat(background-task): disable tools in child sessions

Background task tool이 child session을 생성할 때 background_task, background_output, background_cancel 도구를 자동으로 비활성화합니다. OpenCode Task tool 패턴과 동일하게 무한 재귀 호출을 방지합니다.

- manager.ts: promptAsync 호출 시 tools 설정 추가
- index.ts: 불필요한 agent 레벨 disable 설정 제거 (manager에서 처리)
- notification: tool calls 카운트 제거 (정확하게 트래킹되지 않음)

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/features/background-agent/manager.ts

@@ -77,6 +77,11 @@ export class BackgroundManager {
       path: { id: sessionID },
       body: {
         agent: input.agent,
+        tools: {
+          background_task: false,
+          background_output: false,
+          background_cancel: false,
+        },
         parts: [{ type: "text", text: input.prompt }],
       },
     }).catch((error) => {
@@ -215,7 +220,6 @@ export class BackgroundManager {
 
   private notifyParentSession(task: BackgroundTask): void {
     const duration = this.formatDuration(task.startedAt, task.completedAt)
-    const toolCalls = task.progress?.toolCalls ?? 0
 
     log("[background-agent] notifyParentSession called for task:", task.id)
 
@@ -232,7 +236,7 @@ export class BackgroundManager {
       }).catch(() => {})
     }
 
-    const message = `[BACKGROUND TASK COMPLETED] Task "${task.description}" finished in ${duration} (${toolCalls} tool calls). Use background_output with task_id="${task.id}" to get results.`
+    const message = `[BACKGROUND TASK COMPLETED] Task "${task.description}" finished in ${duration}. Use background_output with task_id="${task.id}" to get results.`
 
     const mainSessionID = getMainSessionID()
     if (!mainSessionID) {

src/index.ts

@@ -206,14 +206,12 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
         config.agent.explore.tools = {
           ...config.agent.explore.tools,
           omo_task: false,
-          background_task: false,
         };
       }
       if (config.agent.librarian) {
         config.agent.librarian.tools = {
           ...config.agent.librarian.tools,
           omo_task: false,
-          background_task: false,
         };
       }