Allow scrolling through the current conversation history

Describe the feature or problem you'd like to solve

● Describe the feature or problem you'd like to solve ┃ In Copilot CLI, using the mouse wheel or PageUp/PageDown navigates through prompt history instead of scrolling the ┃ current conversation. ┃ ┃ When the conversation becomes long, I cannot scroll up to review earlier messages at the top of the same ┃ conversation. This makes it difficult to refer back to previous requirements, responses, and context.

Proposed solution

Provide a way to scroll through the current conversation independently from prompt-history navigation.
Mouse-wheel scrolling and PageUp/PageDown should scroll the conversation view, while prompt-history navigation
should use separate configurable keybindings.

Example prompts or workflows

No response

Additional context

1. Have a long conversation with multiple prompts and responses.
2. Scroll upward to review messages from earlier in the same conversation.
3. Use PageUp/PageDown to move through the conversation history.
4. Use separate keys when navigating previously entered prompts.

Copilot CLI の入力処理と conversation-view における mouse-wheel および PageUp/PageDown イベントの処理から始めます。現在これらのキーがどのようにプロンプト履歴を移動するかを追跡し、既存のキーバインド設定を特定します。完了条件は、スクロールによって現在の会話内の以前のメッセージを確認でき、プロンプト履歴の移動には別の設定可能なキーを使用することです。