Catch-all commit for outstanding pre-existing local changes. Mixes
several themes that would normally be split:
- Rename: UxPlugin → XPlugin across iOS, macOS, Android registrants.
- New top-level packages under lib/src/: anim/ (animated values,
panes, sheets, dock, measured), core/ (Emitter, ReactiveBuilder
scaffolding, presenter/widget/value/dispose primitives), navi/
(Screen/ScreenStack/Router/hero/transitions), reactive/.
- Edits across existing plugins (clipboard, crash, file, gallery,
keyboard, scanner, sensor, url) to align with the new core.
- Test updates and CHANGELOG/README touches accompanying the above.
