The Toolbar and Sidebar Save buttons wired onClick={onSave} directly, so
React passed the MouseEvent as the first argument. handleSave treats its
first arg as a designIdOverride, corrupting design_id and making the save
fail silently. Ctrl+S worked because it calls handleSave() with no args.
Wrap both handlers as onClick={() => onSave()} so no event leaks through.
Add regression tests asserting onSave is called with zero arguments.
Fixes#186
ha-relevant: no
Pouzor