Adds hydration cursor to render pipeline:
- boot.sx: *hydrating* flag, hydrate-start!/stop!, cursor stack helpers
- adapter-dom.sx: render-dom-element uses existing SSR elements when
*hydrating* is true. Text nodes reused. dom-append skipped.
- hydrate-island: calls hydrate-start! before render-to-dom, no
replaceChildren. SSR DOM stays in place.
Status: screenshots identical (no visual flash), but event listeners
not attaching — the cursor/set! interaction between CEK and VM needs
debugging. The hydrate-start! set! on *hydrating* may not propagate
to the bytecoded adapter-dom render path.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
0044f17e4c