[Feature Request] Add silent mode for copy-on-select toast notification

Bug Description
Fullscreen renderer, iTerm2 on macOS, v2.1.241.

Please add a way to keep copy-on-select while silencing the "copied N chars to clipboard" toast.
iTerm2's own copy-on-select is silent, and after many years of that muscle memory the toast fires on
every single selection and pulls my eye away from what I was reading.

Today /config only toggles copy-on-select as a whole, and the one silent path left is turning it off
and holding Option for native selection - which is not realistic to relearn. A settings key (e.g.
copyOnSelectToast: false) or a third state in /config would solve it.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.241
• Feedback ID: 5e41c7b3-3faf-4eba-9a23-ec3845d56538