Home page stepper: reactive code view with syntax colouring where
tokens highlight as you step through DOM construction. Each token
is a span with signal-driven classes — current step bold+violet,
completed steps dimmed, upcoming normal. CSSX styling via ~cssx/tw
spreads. Lake preserves imperative DOM across reactive re-renders.
Also fixes: bare lowercase 'nil' in platform_js.py eventDetail and
domGetData — should be NIL (the SX sentinel object).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>