Improve large Copy/Paste text

### Describe the feature or problem you'd like to solve

Display first 1 or 2 lines whenc "Copy paste"

### Proposed solution

It'd be helpfull if Copilot CLi could show the first 1 or 2 lines when pasting large texts, so rather than

```
[Paste #1 - 133 lines]
```

show this:

```
Please generate a Monday report....
[Paste #1 - 132 lines]
```

### Example prompts or workflows

_No response_

### Additional context

_No response_

Start by locating the Copy/Paste handling that formats large pasted text, then reproduce the behavior with a multiline input. Done means large pastes show their first one or two lines before the paste marker, with the displayed line count adjusted consistently.

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