Feature Request: submitOnEnter setting for Enter key behavior

Summary

Add official support for a keyboard.submitOnEnter: false setting to make Enter key insert a newline instead of submitting the prompt.

Current Behavior

• Enter key submits the prompt immediately
• Users must use Shift+Enter or backslash+Enter for multiline input
• A keyboard.submitOnEnter setting exists in settings.local.json but has no effect

Requested Behavior

• When keyboard.submitOnEnter: false is set:
• Enter inserts a newline
• Ctrl+Enter (or Cmd+Enter on macOS) submits the prompt
• This matches behavior of Slack, Discord, and many other chat/text applications

Use Case

Many users prefer composing longer prompts with natural Enter key usage, especially when writing code blocks or detailed instructions. The current behavior interrupts the natural typing flow.

Environment

• CLI (terminal)
• Tested with settings.local.json containing:

{
  "keyboard": {
    "submitOnEnter": false
  }
}

Thank you for considering this feature!