gpui-component-dev

Create a new file in crates/ui/src following existing patterns like Button or Select, register the module in lib.rs, and use the builder pattern for configuration. Choose stateless, stateful, or composite design based on complexity, then add a story and documentation.

Create a story file in crates/story/src/stories implementing the Story trait with title and new_view methods, organize examples with section! calls, and register it in stories/mod.rs and the story list in main.rs. Cover all variants, states, and edge cases.

Use stateless elements for simple presentation components like Button, and stateful elements for components managing their own data like Select with SelectState. Use composition when building on existing components, such as AlertDialog built on Dialog.

Add a ## Breaking Changes section only when crates/ui public APIs change. List each change as a bullet with a title and a diff code block showing old versus new usage, and use ### subsections for large migrations with multiple paths.

Add a StyleRefinement field, implement the Styled trait returning &mut self.style, and call .refine_style(&self.style) on the root element in render(). Place it after default styles but before children so user styles override defaults.