Add keybinding support for controlling inline ghost text (accept/dismiss) in Chat

Feature Request

Currently there's no way to control inline ghost text suggestions in the chat input via keybindings. The Autocomplete context keybindings don't appear to affect ghost text — only dropdown-style autocomplete.

Desired Behavior

A dedicated action (e.g. ghostText:accept, ghostText:dismiss) would allow users to:

• Prevent enter from accepting ghost text while still using it to submit messages
• Optionally rebind ghost text acceptance to a different key (e.g. tab)

Current Workaround

None. Setting enter: null in the Autocomplete context does not affect ghost text behavior.