gui_toolkit 0.120.0

Added

• prefs_page: a program's settings page from its config registry, with no code per preference, in the look of opencode native's settings: the search in a well and the pages with their icons on the left; the page's title and a line per preference on the right (its title and description, a switch, a segmented choice or a list, a slider or a field with its unit, a reset button, a carved line); a search shows what matches in every page. Options.custom gives a preference a control of the program's own; theme_cards shows the themes as cards in their own colours. Options.changed runs after each change, for the program to save and apply it. See docs/prefs_page.md.