Three new interactions:
1. Route hover → chart: Invisible interactive polyline (weight 20,
opacity 0) detects mouse hover on the route, computes cumulative
distance, and highlights the corresponding position on the chart.
2. Chart click → map pan: Clicking the elevation chart pans the map
to center on that point along the route. Uses 5px threshold to
distinguish from drag.
3. Chart drag-select → map zoom: Dragging a range on the chart shows
a blue selection overlay, then zooms the map to fit the route
coordinates in that range. "Reset zoom" button appears to restore
the full route view.
State flow avoids feedback loops: external highlights (from map hover)
set the chart crosshair without re-emitting onHover back to the map.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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