Common component contracts

All 23 components declare these five fields directly in their Props; there is no nested common-props wrapper.

Field	Purpose, defaults, and constraints	Example
Key string	Empty matches by type/position within one parent; nonempty keys must be stable and unique among siblings. Moving to another parent does not retain identity.	State and identity
Style Style	Zero selects defaults; local dimensions, spacing, and painting.	Styles
Token ComponentToken	Defaults to the component theme entry; an explicit value selects another defined entry.	Themes
States StateStyles	Paint patches for actual interaction states; does not create states or change layout.	Precedence
Pointer PointerBehavior	Defaults to PointerAuto; PointerNone excludes the whole subtree from pointer participation. Not a generic Disabled flag.	Layout and hit testing

Constructors return immutable View descriptions, not mutable widgets. View.WithKey(string) and View.WithStyle(Style) return independent descriptions; WithStyle replaces the entire Style. A zero View is invalid as a root or child; an empty Box is valid.

Events run on the UI thread. Nil callbacks have component-specific meanings and do not imply Disabled. The runtime owns hover, focus, press, IME composition, overlays, and uncontrolled scrolling. The application owns values such as Value/Checked/Open. See state and examples.

See component declarations for structs, enums, and functions, and style declarations for shared Style and theme structures.