Clang-format sees the text behind `#pragma region` as code and formats it. Instead of stating the copyright and date there, it's now in the comment block right below it. The text "Copyright" is left in the `#pragma region` line, as clang-format sees it as a single identifier.
I took the opportunity to normalize the dates, and add the copyright notice to the source files where it was missing them (except for third-party and the generated resources.h file).
Create a dummy UI context and use that if headless is enabled. Some extra guards added to deal with the return values from the dummy class. It may be temporary until the window and input code is moved to openrct2ui.