Platform:
- sx-platform.js: extract ?v= query from script tag URL, append to
all .sx file XHR requests. Prevents stale cached .sx files.
Stepper performance:
- do-back: use rebuild-preview (pure SX→DOM render) instead of
replaying every do-step from 0. O(1) instead of O(n).
- Hydration effect: same rebuild-preview instead of step replay.
- Cookie save moved from do-step to button on-click handlers only.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
