Add Ctrl+D to exit when editor is empty

- Add isCtrlD helper to keys.ts
- CustomEditor intercepts Ctrl+D and only triggers callback when editor is empty
- Single Ctrl+D with empty input exits immediately
- Update CHANGELOG to frame as feature (Kitty protocol support) not fix

packages/tui/src/index.ts

@@ -23,6 +23,7 @@ export {
 	isAltBackspace,
 	isCtrlA,
 	isCtrlC,
+	isCtrlD,
 	isCtrlE,
 	isCtrlK,
 	isCtrlO,