Three fixes:
1. Framework: render-dom-lake preserves SSR elements during hydration.
When client-side render-to-dom encounters a lake with an existing
DOM element (from SSR), it reuses that element instead of creating
a new one. This prevents the SSR HTML from being replaced with
unresolvable raw SX expressions (~tw calls).
2. Stepper: skip rebuild-preview on initial hydration. Uses a non-
reactive dict flag (not a signal) to avoid triggering the effect
twice. On first run, just initializes the DOM stack from the
existing SSR content by computing open-element depth from step
types and walking lastElementChild.
3. Stepper: rebuild-preview computes correct DOM stack after re-render.
Same depth computation + DOM walk approach. This fixes the bug where
do-step after do-back would append elements to the wrong parent
(e.g. "sx" span outside h1).
Also: increased code view font-size from 0.5rem to 0.85rem.
Playwright tests:
- lake never shows raw SX during hydration (mutation observer)
- back 6 + forward 6 keeps all 4 spans inside h1
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>