Plan mode is actually implementing and making code changes

### Describe the bug

while in "Plan" mode , copilot is making code changes, that should not happen in any case.

### Affected version

latest as of right now

### Steps to reproduce the behavior

go into plan mode, tell copilot to do some "simple" changes, it will do them, instead of making a plan.

### Expected behavior

even if the plan is simple, it should create it, not just go ahead and implement it.

### Additional context

_No response_

No file, test, or entry point is named in the report. Start by reproducing the behavior in Copilot CLI's Plan mode with a simple requested change, then trace the Plan mode flow. Done means Plan mode produces a plan without applying code changes.

Written by the indexing model from the issue text.