Fix findUsages/undo/node-lookup bugs, split Viewport and Editor, share command and inspector helpers

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ui/math.ts

@@ -7,3 +7,12 @@ export function clamp(value: number, lo: number, hi: number): number {
 export function centreY(containerHeight: number, itemHeight: number): number {
   return Math.round((containerHeight - itemHeight) / 2);
 }
+
+/**
+ * Zoom multiplier for one wheel event. Exponential, so scrolling up and back down by the same
+ * amount lands exactly where it started. The caller clamps the result into its own range –
+ * the scene view and the graph editor allow very different zoom levels.
+ */
+export function zoomFactor(deltaY: number): number {
+  return Math.exp(-deltaY * 0.0015);
+}