fix: dragging now switches source unit to update all bars correctly

Fixed dragging behavior so all bars update when you drag:

Problem:
- Dragging a bar would change values but bars wouldn't visually update
- The bar would reset to original length on release
- Other bars wouldn't change at all

Root cause:
- We were converting the dragged value back to the selected unit
- This kept the source unit the same, so relative percentages didn't change
- The logarithmic scale maintained proportions, preventing visual updates

Solution:
- When dragging a bar, switch to that unit as the new source unit
- Set both inputValue and selectedUnit to the dragged unit's value/name
- This changes the conversion base, making all other bars recalculate
- Removed draggedPercentage state (not needed with this approach)
- All bars now use calculated percentages from conversions

How it works now:
- Drag the "feet" bar → becomes the source unit (selectedUnit = 'ft')
- All conversions recalculate from feet
- All bars update their percentages based on new conversion base
- No transitions during drag for instant visual feedback
- Smooth animation when drag ends

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/converter/MainConverter.tsx

@@ -125,11 +125,10 @@ export default function MainConverter() {
 
   // Handle value change from draggable bars
   const handleValueChange = useCallback((value: number, unit: string) => {
-    // Convert the dragged unit's value back to the currently selected unit
-    const convertedValue = convertUnit(value, unit, selectedUnit);
-    setInputValue(convertedValue.toString());
-    // Keep selectedUnit the same - user is still inputting in that unit
-  }, [selectedUnit]);
+    // When dragging a bar, switch to that unit as the source
+    setInputValue(value.toString());
+    setSelectedUnit(unit);
+  }, []);
 
   return (
     <div className="w-full max-w-6xl mx-auto space-y-6">

components/converter/VisualComparison.tsx

@@ -16,7 +16,6 @@ export default function VisualComparison({
   onValueChange,
 }: VisualComparisonProps) {
   const [draggingUnit, setDraggingUnit] = useState<string | null>(null);
-  const [draggedPercentage, setDraggedPercentage] = useState<number | null>(null);
   const dragStartX = useRef<number>(0);
   const dragStartWidth = useRef<number>(0);
   const activeBarRef = useRef<HTMLDivElement | null>(null);
@@ -101,9 +100,6 @@ export default function VisualComparison({
     let newPercentage = dragStartWidth.current + deltaPercentage;
     newPercentage = Math.max(3, Math.min(100, newPercentage));
 
-    // Update the visual percentage immediately
-    setDraggedPercentage(newPercentage);
-
     // Find the conversion result for this unit
     const conversion = conversions.find(c => c.unit === draggingUnit);
     if (!conversion) return;
@@ -121,7 +117,6 @@ export default function VisualComparison({
 
   const handleMouseUp = useCallback(() => {
     setDraggingUnit(null);
-    setDraggedPercentage(null);
     activeBarRef.current = null;
   }, []);
 
@@ -148,9 +143,6 @@ export default function VisualComparison({
     let newPercentage = dragStartWidth.current + deltaPercentage;
     newPercentage = Math.max(3, Math.min(100, newPercentage));
 
-    // Update the visual percentage immediately
-    setDraggedPercentage(newPercentage);
-
     const conversion = conversions.find(c => c.unit === draggingUnit);
     if (!conversion) return;
 
@@ -165,7 +157,6 @@ export default function VisualComparison({
 
   const handleTouchEnd = useCallback(() => {
     setDraggingUnit(null);
-    setDraggedPercentage(null);
     activeBarRef.current = null;
   }, []);
 
@@ -199,8 +190,6 @@ export default function VisualComparison({
       {withPercentages.map(item => {
         const isDragging = draggingUnit === item.unit;
         const isDraggable = !!onValueChange;
-        // Use dragged percentage if this bar is being dragged, otherwise use calculated percentage
-        const displayPercentage = isDragging && draggedPercentage !== null ? draggedPercentage : item.percentage;
 
         return (
           <div key={item.unit} className="space-y-1.5">
@@ -241,14 +230,14 @@ export default function VisualComparison({
                   draggingUnit ? "transition-none" : "transition-all duration-500 ease-out"
                 )}
                 style={{
-                  width: `${displayPercentage}%`,
+                  width: `${item.percentage}%`,
                   backgroundColor: color,
                 }}
               />
               {/* Percentage label overlay */}
               <div className="absolute inset-0 flex items-center px-3 text-xs font-bold pointer-events-none">
                 <span className="text-foreground drop-shadow-sm">
-                  {Math.round(displayPercentage)}%
+                  {Math.round(item.percentage)}%
                 </span>
               </div>