Zoom and pan the preview with the wheel, and step a parameter from its ruler

Cursor over the image: the wheel zooms about the pointer, and a drag pans,
both clamped to the contain-fit of the loaded bitmap so the photo can never
be lost off-screen. Cursor over an open parameter ruler: the wheel moves that
parameter by one step, clamped to its min/max. While the crop frame is being
dragged the wheel keeps resizing the crop instead, and APPLY puts the view
back on the fit.

docker/frontend/src/ui/ChipColumn.tsx

@@ -1,3 +1,5 @@
+import { useEffect, useRef } from 'react';
+
 // One strip at a time — the same shape as the phone's AdjustmentPanel: a ruler
 // row for the open slider, an options strip for the open group, then the tab's
 // chip row. Chip labels are the phone's own strings (they are not translated
@@ -53,8 +55,27 @@ export function ChipRow({ chips }: { chips: ChipDef[] }) {
 }
 
 export function SliderRow({ slider }: { slider: SliderDef }) {
+  // The wheel belongs to the open ruler: one notch is one step, held inside the
+  // parameter's own range. The listener is native because React's is passive —
+  // the panel must not scroll away under the cursor while the value moves.
+  const rowRef = useRef<HTMLDivElement>(null);
+  const live = useRef(slider);
+  live.current = slider;
+  useEffect(() => {
+    const el = rowRef.current;
+    if (!el) return;
+    const onWheel = (e: WheelEvent) => {
+      e.preventDefault();
+      const s = live.current;
+      const step = s.step || 1;
+      const next = Math.min(s.max, Math.max(s.min, s.value + (e.deltaY < 0 ? step : -step)));
+      if (next !== s.value) s.onChange(next);
+    };
+    el.addEventListener('wheel', onWheel, { passive: false });
+    return () => el.removeEventListener('wheel', onWheel);
+  }, []);
   return (
-    <div className="slider-row">
+    <div className="slider-row" ref={rowRef}>
       <button type="button" className="back" onClick={slider.onBack} aria-label="back">&lt;</button>
       <div className="ruler">
         <div className="head">