fix(aibox): batch I audit fixes - prompt write cap, light-subagent cancel propagation, atomic history writes

Remaining-item sweep (audit report §12):
- N9: cap prompt file writes (identity/soul/status, 10k chars) to bound
  persistent-injection surface
- F5: run_light_subagent switches to stream_chat + parent cancel_event
  (mid-stream interrupt); ExpressEmotionTool injects parent event
- Q4: busy_timeout=10s on mark_as_triggered (multi-process DB contention)
- Q5: malformed reminder_time tasks returned as due (were silently dropped
  by SQL-level string filter, which is now Python-side authoritative check)
- Q7b: load_conversation realpath prefix check (../ traversal defense)
- Q8: atomic JSON writes (tmp+os.replace) for index/current/archive
- F6: dedicated ws command executor for /new, /reload_prompts
- F9: --once hard-exit backstop after soft timeout
- PromptManager singleton lock; limit=0 semantics (None = no LIMIT)

aibox/tools/prompt_tools.py

@@ -56,6 +56,11 @@ class UpdateIdentityTool(Tool):
         if not content:
             return "❌ 需要提供身份信息内容"
 
+        # N9：持久化注入面约束——内容超限拒绝写入（管理端另有兜底）
+        if len(content) > PromptManager.MAX_CONTENT_LENGTH:
+            return (f"❌ 内容过长（{len(content)} > {PromptManager.MAX_CONTENT_LENGTH} 字符），"
+                    f"身份文件作为系统提示词加载，请精简后重试")
+
         if not confirm:
             return "❌ 身份更新已取消，如需更新请设置 confirm=true"
 
@@ -119,6 +124,11 @@ class UpdateSoulTool(Tool):
         if not content:
             return "❌ 需要提供智能体自我认识定义内容"
 
+        # N9：持久化注入面约束——内容超限拒绝写入（管理端另有兜底）
+        if len(content) > PromptManager.MAX_CONTENT_LENGTH:
+            return (f"❌ 内容过长（{len(content)} > {PromptManager.MAX_CONTENT_LENGTH} 字符），"
+                    f"灵魂文件作为系统提示词加载，请精简后重试")
+
         if not confirm:
             return "❌ 自我认识更新已取消，如需更新请设置 confirm=true"
 
@@ -223,6 +233,11 @@ class SaveMemoryAndEndConversationTool(Tool):
             status_content += f"【下一步计划】\n{next_goals}\n\n"
         status_content += f"【对话总结】\n{summary}"
 
+        # N9：状态文件作为系统提示词加载，超长拒绝写入（约束注入规模）
+        if len(status_content) > PromptManager.MAX_CONTENT_LENGTH:
+            return (f"❌ 状态内容过长（{len(status_content)} > "
+                    f"{PromptManager.MAX_CONTENT_LENGTH} 字符），请精简 current_status/summary 后重试")
+
         # 更新状态文件
         status_updated = self.prompt_manager.update_status(status_content)