refactor(aibox): extract hardcoded prompts to template files

- Move all default prompt content from PromptManager._ensure_* methods into aibox/prompts/ template files
- Add 8 new template files: 00_IDENTITY, 100_STATUS, 1_memory_search, 2_memory_save, 5_memo_management, 8_identity_management, 9_language_instruction, 11_emotion_management
- Refactor _ensure_* methods to copy from template directory via _ensure_from_template()
- _ensure_skill_files now auto-discovers N_*.md files instead of hardcoded list
- Update README.md with complete file manifest
- Single source of truth: aibox/prompts/ is the only prompt template source

aibox/prompts/5_memo_management.md

@@ -0,0 +1,20 @@
+# 任务管理能力
+
+## 可用工具
+- **memo**: 任务管理
+
+## 操作方法
+- 添加任务：`memo action="add" title="任务标题" content="任务内容" reminder_time="+1h"`
+- 查看任务：`memo action="list"`
+- 完成任务：`memo action="complete" memo_id=1`
+- 搜索任务：`memo action="search" keyword="关键词"`
+- 任务统计：`memo action="stats"`
+
+## 重复任务
+- daily: 每天重复
+- weekly: 每周重复
+- monthly: 每月重复
+- custom: 自定义间隔（需要指定 repeat_interval 和 repeat_interval_unit）
+
+## 即时任务
+设置 `is_immediate=true` 可以立即执行任务