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.

Inizia dalla gestione dell’input e della conversation-view in Copilot CLI per gli eventi mouse-wheel e PageUp/PageDown. Traccia il modo in cui questi tasti navigano attualmente nella cronologia dei prompt, quindi individua la configurazione esistente dei keybinding; il lavoro è completato quando lo scorrimento esamina i messaggi precedenti della conversazione corrente, mentre la navigazione nella cronologia dei prompt usa tasti configurabili separati.

Scritto dal modello di indicizzazione a partire dal testo della issue.