- per-run checkbox when embedding HTML exists; cap at 2 selected
- sticky 'compare selected' button opens /compare?a=&b= in new tab
- selection state persists across the 3s htmx poll via a Set keyed by stem
- /compare stub validates stems, renders scaffolding (three.js UI next)
Three short paragraphs framing what the notebook studies: stability of
2-D embeddings under controlled perturbation of the input over time,
the two metrics logged per run, and why the streaming/longitudinal
angle matters for both visualization and downstream classification.
