Some Copilot CLI base instructions issued to a subagent prevent it from writing output to a file

### Describe the bug

- I created a set of agents forming an orchestrator pattern for the full Work Item implementation
- When orchestrator executes a subagent responsible for functional testing this subagent consistently reports that it either could not write a test result file or was **instructed not to write output to a file**
- In either orchestrator or functional tester there are absolutely no instructions to prevent writing output files
- Orchestrator invokes the functional testing subagent only with the Work Item ID (no other `runSubagent` additional instructions)
- In other subagents for phases like Implementation everything works perfectly fine

Sample response from functional testing subagent (**GPT 5.3 Codex**) "...but I could not write the required notes file due the active session constraint: “Do NOT write output to files.”"

Related bug report: #3049
### Affected version

_No response_

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

The same workflow works 100% fine when run via VS Code.

先從此處描述的 orchestrator 和 functional-testing subagent 流程開始，然後將其行為與 VS Code 中的相同工作流程進行比較，並檢視相關 bug #3049。僅使用一個 Work Item ID 重現 Functional Tester，並驗證它不再收到禁止寫入輸出檔案的指令，且能夠建立所需的測試結果檔案。

由索引模型根據 Issue 內容生成。