fix: reverse slice slider and scroll direction for anatomical consisency

src/components/SliceSlider.vue

@@ -72,7 +72,9 @@ export default {
   computed: {
     handlePosition() {
       const range = this.max - this.min <= 0 ? 1 : this.max - this.min;
-      const pos = this.maxHandlePos * ((this.modelValue - this.min) / range);
+      // Invert mapping: lower slice numbers at bottom for anatomical consistency
+      const pos =
+        this.maxHandlePos * (1 - (this.modelValue - this.min) / range);
       return this.dragging ? this.draggingHandlePos : pos;
     },
     draggingHandlePos() {
@@ -148,7 +150,8 @@ export default {
     },
 
     getNearestSlice(pos) {
-      const sliceEstimate = pos / this.maxHandlePos;
+      // Invert position: bottom of slider = lower slice numbers
+      const sliceEstimate = 1 - pos / this.maxHandlePos;
       const frac = sliceEstimate * (this.max - this.min) + this.min;
       return Math.round(frac / this.step) * this.step;
     },

src/components/vtk/VtkSliceViewSlicingManipulator.vue

@@ -54,7 +54,8 @@ const scroll = useMouseRangeManipulatorListener(
   'scroll',
   sliceConfig.range,
   1,
-  sliceConfig.slice.value
+  sliceConfig.slice.value,
+  -1 // Invert scroll: scroll down = decrease slice for anatomical consistency
 );
 
 watch(scroll, () => {

src/core/vtk/useMouseRangeManipulatorListener.ts

@@ -14,7 +14,8 @@ export function useMouseRangeManipulatorListener(
   type: ListenerType,
   range: MaybeRef<Maybe<[number, number]>>,
   step: MaybeRef<Maybe<number>>,
-  initialValue?: number
+  initialValue?: number,
+  scale: number = 1 // Negative scale inverts scroll direction
 ) {
   const internalValue = ref(initialValue ?? 0);
 
@@ -37,7 +38,8 @@ export function useMouseRangeManipulatorListener(
         () => internalValue.value,
         (val) => {
           internalValue.value = val;
-        }
+        },
+        scale
       );
 
       onCleanup(() => {