Two bugs fixed:
1. Hydration flash: The effect's schedule-idle called rebuild-preview
on initial hydration, which cleared the SSR HTML and re-rendered
(flashing raw SX source or blank). Fix: skip rebuild-preview on
initial render — the SSR content is already correct. Only rebuild
when stepping.
2. Stepping structure: After do-back calls rebuild-preview, the DOM
stack was reset to just [container]. Subsequent do-step calls
appended elements to the wrong parent (e.g. "sx" span outside h1).
Fix: compute the correct stack depth by replaying open/close step
counts, then walk the rendered DOM tree that many levels deep via
lastElementChild to find the actual DOM nodes.
Proven by harness test: compute-depth returns 3 at step 10 (inside
div > h1 > span), 2 at step 8 (inside div > h1), 0 at step 16 (all
closed).
Playwright test: lake never shows raw SX (~tw, :tokens) during
hydration — now passes.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
b13962e8dd