fix(cli): clear input buffer after /model picker selection

The Enter handler that confirms a selection in the /model picker closed
the picker but never reset event.app.current_buffer, leaving the user's
original "/model" command lingering in the prompt. Match the ESC and
Ctrl+C handlers (which already reset the buffer) so the prompt is empty
after a successful switch.

cli.py

@@ -8556,6 +8556,7 @@ class HermesCLI:
             # --- /model picker modal ---
             if self._model_picker_state:
                 self._handle_model_picker_selection()
+                event.app.current_buffer.reset()
                 event.app.invalidate()
                 return