- signals.sx: add def-store/use-store/clear-stores (L3 named stores)
and emit-event/on-event/bridge-event (lake→island DOM events)
- reactive-islands.sx: add event bridge, named stores, and plan pages
- Remove ~plan-reactive-islands-content from plans.sx
- Update nav-data.sx and docs.sx routing accordingly
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>