Sketch in assistant edit button (#19705)

Add an edit button to the assistant. This is totally hacked in for now,
just to see how this would feel rendered simply in the UI.

![CleanShot 2024-10-24 at 16 26
14@2x](https://github.com/user-attachments/assets/e630d078-78b7-42d7-93f1-cf61c00bd20e)

cc @as-cii @danilo-leal 

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <67129314+danilo-leal@users.noreply.github.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>

assets/keymaps/default-linux.json

@@ -532,6 +532,7 @@
     "context": "ContextEditor > Editor",
     "bindings": {
       "ctrl-enter": "assistant::Assist",
+      "ctrl-shift-enter": "assistant::Edit",
       "ctrl-s": "workspace::Save",
       "ctrl->": "assistant::QuoteSelection",
       "ctrl-<": "assistant::InsertIntoEditor",