Input and Gestures in Reactor

Reactor exposes input via trampoline-dispatched .On* modifiers. Events auto-enable their underlying WinUI flags (ManipulationMode, AllowDrop, etc.) when you attach a handler, so you never need to set those manually.

Controlled prop note: input factories keep the ergonomic (value, setter) shape. The underlying controlled element properties are Optional<T> so Unset can mean "control-owned"; direct reads need .Value or .GetValueOrDefault(...). See migration/050-optional-t.md.

Quick reference