Fix expansion (ctrl+o) making Terminator terminal go blank and scroll to top of the buffer

### What happened?

Hi all,
I have been using plan mode a little bit and have an issue that's really annoying, but probably quite a quick fix. Here's what happens. Everything is fine up until step 4:

1) I type /plan and press enter
2) I type a feature I want to implement with as much info as possible
3) The model looks at the code and processes its ideas
4) I am asked the question of whether I want to go ahead with the plan.

At step 4, the plan is not shown but I can press CTRL+O to see the full text. It is not clear at this point where the plan is saved on disk so I must press this to see what it has done.

Unfortunately, in this expanded state, the terminal immediately goes blank, then scrolls all the way up to the top of the buffer. I am using the Terminator terminal.

If I scroll down to see the plan, this "scroll to the top" behaviour happens every few seconds automatically, so the scroll position is lost and I have to scroll back down to see the plan.

Therefore, it is impossible to read the plan in the terminal and I must approve the plan and then immediately stop processing by pressing Esc. Once doing so, the location of the plan is shown and is in an obscure path, so difficult to find. Opening this .md file in my editor is the only way to view it. If there are any changes needed to it, things become problematic because I have already accepted the plan and am no longer in plan mode. The whole point of plan mode should be to have a back & forth conversation to optimize the plan and correct any mistakes, but accepting the plan seems to confuse the model if I wish to make any tweaks.

So, often I have to start a fresh context window, feeding in the current .md file and telling it to tweak that plan.

### What did you expect to happen?

If the terminal viewing experience of the plan didn't have this odd behaviour, things would be much easier.

### Client information

Client Information

Run `gemini` to enter the interactive CLI, then run the `/about` command.

```console
> /about
│ About Gemini CLI │
│ │
│ CLI Version 0.31.0 │
│ Git Commit 72c653354 │
│ Model gemini-3-flash-preview │
│ Sandbox no sandbox │
│ OS linux │
│ Auth Method Logged in with Google ([redacted]@gmail.com) │
│ Tier Gemini Code Assist for individuals
```

### Login information

_No response_

### Anything else we need to know?

_No response_