[Bug] Agent attempts file modifications while still in Plan Mode

提交前确认 · Pre-submission checklist

• 我已搜索过现有 issue，确认这不是重复 / I searched existing issues and confirmed this isn't a duplicate.
• 我已阅读 CONTRIBUTING.md / I've read CONTRIBUTING.md.

问题类别 · Category

文件 / 项目操作 · File / Project ops

涉及的 Agent 框架 · Agent framework

ZCode Agent（自研）

严重程度 · Severity

影响体验 · Major (功能可用但体验受损 / works but degraded)

复现频率 · Reproducibility

偶现 · Sometimes

问题描述 · Description

In ZCode Desktop, the Agent sometimes attempts to modify files or perform other write-related actions while the UI is still clearly in Plan Mode.

This happens without manually switching modes and without the Agent exiting Plan Mode first.

Since Plan Mode is expected to remain read-only until the plan is completed and the mode is explicitly exited, the Agent should not attempt Edit, Write, or other state-changing operations at this stage.

复现步骤 · Steps to reproduce

Open a project in ZCode Desktop.
Switch the Agent to Plan Mode.
Give it a task that will eventually require file modifications.
Let it inspect the project and prepare a plan.
Occasionally, before Plan Mode is exited, the Agent starts attempting file modifications or write-related operations while the UI still shows Plan Mode.

期望表现 · Expected behavior

While Plan Mode is active, the Agent should:

remain read-only;
inspect and analyze the project;
produce or refine the implementation plan;
avoid all file modifications and other state-changing operations;
exit Plan Mode before starting implementation.

实际表现 · Actual behavior

The Agent occasionally behaves as if it has already entered execution mode and attempts to modify files even though:

the UI still shows Plan Mode;
no manual mode switch occurred;
Plan Mode was not explicitly exited.

ZCode 版本 · ZCode version

v3.11.2

设备 / 系统 / 浏览器 · Device / OS / Browser

windows 10

截图 / 录屏 / 日志 · Screenshots / Recordings / Logs

No response

Start by reproducing the issue in ZCode Desktop on Windows 10 with Plan Mode enabled and a task that eventually requires file changes. Trace the transition from Plan Mode to execution and the write-related actions; done means the Agent remains read-only until Plan Mode is explicitly exited.