recap/bin/slides.mjs: setContent waitUntil=domcontentloaded
networkidle0 sometimes hangs on oven for slides with multi-MB base64
photos embedded inline (build 67f9ee23-8 timed out at slide 07_hp_plotter
after rendering 6 slides successfully). domcontentloaded fires once the
DOM is parsed, which is all we need before screenshot — data URLs render
synchronously, no network to wait on. 90s timeout for slow CPU safety.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>