CI: add brackets to one-line blocks

- since we mix Python (indentation is important) with C++ (it isn't),
   having indented one-line blocks which suddenly need {} when a
   statment is added is confusing and error-prone. Instead, make
   the blocks explicit, always, in C++.

ci/astylerc

@@ -5,7 +5,7 @@ indent=spaces=4
 
 # Brackets
 style=break
-remove-brackets # Remove brackets on single-line `if` and `for` (requires astyle 2.04)
+add-brackets
 
 # Spaces
 pad-paren-in