IPriceLine has no native click event, so use a coordinate-matching pattern:
- On Alt+Click, compute candle.priceToCoordinate for each hline
- Find the one whose y is closest to the click y
- If within ±6px, remove it via removeLine
Complements the chips ✕ button — clicking the line itself on the chart is
more natural than aiming at a small ✕. Shift+Click for add still wins when
both modifiers are held (more frequent, checked first).
- StockChart toolbar title and ShortcutsHelp updated to surface the gesture
7312d0aadc