Per Justin: a round's dots no longer start fading together. Every node
gets a deterministic random appearance moment inside the first 70% of
the round interval (the rest is its fade), and a new roundProgress
value, driven by the playback frame loop, feeds the same jitter into
the panel stats: the big percentage and reached count now tick up
exactly as dots start appearing, in the cards, the mobile strip, and
the focus modal. Pausing, stepping, and seeking hold the full round;
reduced motion keeps discrete swaps.
Hand-rolled SVG as decided: dashed percent grid, one cumulative curve
per panel in its accent color, end labels via the shared formatPct, and
a playhead line with per-curve dots synced to the global round. The
cumulative-at-round counting moved into lib/reach.ts so the panel stats
and the chart cannot disagree.
