Add screen-clear-only slash command or configurable keybindings

Problem

Ctrl+L clears the terminal screen while preserving conversation history, but this keybinding conflicts with common setups like vim-tmux-navigator where Ctrl+h/j/k/l are used for seamless pane navigation.

The only alternative is /clear, but that also clears conversation history — which is often not desired.

Requested Solution

Either:

1. Add a slash command for screen-clear-only (e.g., /cls or /clear-screen) that clears the visual display without affecting conversation history
2. Allow configurable keybindings so users can remap shortcuts to avoid conflicts

Use Case

Users with vim-tmux-navigator or similar setups use Ctrl+h/j/k/l for navigation across tmux panes and nvim splits. Changing this would break established muscle memory and workflow. A slash command alternative would solve this without requiring keybinding customization.