[BUG] Title: Autocompact buffer persists across /clear — wastes tokens for irrelevant old context

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

when i have finished working on current task, I do /clear and also open a new session.
In the new session, I perform /context and it shows approx 33K tokens under autocompact buffer.
This buffer is not useful for me, as I can build the same context via claude.md and memory files at much cheaper token cost.
This autocompact buffer do the round tripping with every message and it adds to my tokens usage , which is completely avoidable.

What Should Happen?

There should be a way to clear the context completely, so that I can clear all the buffer and save my tokens, if I am starting a completely new task

Error Messages/Logs

Steps to Reproduce

Create a new session under claude code and check /context information under autocompact buffer

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

claude-haiku-4-5-20251001

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_