This should prevent pasting and backspace as well.
Readonly or non-editable text controls block keyboard navigation on the Mac, so make them normal text controls, but block any edits.
In addition, I've extracted the wxTextCtrl wrapper from the TimerRecordDialog intto widgets/wxTextCtrlWrapper.h and made it the default for ShuttleGui::AddTextBox(). This way readonly text controls are always included in the tab order.