/undo does not undo todos

Description

I ran /undo and the todos that were added from the undid run were not reverted. This resulted in my agent to continue to do work that I did not want it to do after I sent it another prompt.

Expected behavior: /undo should restore the todo list to its state before the undone prompt.

Looks like this was attempted to be fixed, but it was never merged: https://github.com/anomalyco/opencode/pull/5516

This appears related to #4081 and #26833, which are closed, and the broader open issue #4704.

Plugins

None

OpenCode version

1.18.26

Steps to reproduce

1. Start a new session
2. Send "create a new todo that says test"
3. Send "/undo"
4. Notice how the test todo created in the first

Screenshot and/or share link

Operating System

Ubuntu 22.04.5 LTS under WSL2

Terminal

Windows Terminal with tmux