Feature request: clear screen display without resetting conversation context

Summary

Add a way to clear the visible terminal output without clearing the conversation context.

Current behavior

• /clear — clears both the screen and conversation context
• Ctrl+L — redraws/refreshes the ncurses display, but doesn't clear scrollback

There is no way to clear just the visible screen while keeping conversation history intact.

Desired behavior

A command like /cls or a keyboard shortcut (e.g. Ctrl+K) that clears the terminal display/scrollback without resetting the conversation.

Use case

During long sessions, the terminal accumulates a lot of output and it becomes hard to find the current working area. Users want to clear the clutter without losing conversation context — similar to how clear works in a regular shell without affecting shell history or state.