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/runtime/systems/CollisionSystem.ts

@@ -1,4 +1,5 @@
 import { isHandleEnabled, worldPositionOf } from '../../core/graph';
+import { parentChain } from '../../core/model/walk';
 import { axisCorrection, colliderShape, colliderSize, isTrigger, type PlaneAxis, shapesOverlap } from '../../core/properties/collider';
 import type { Entity } from '../Entity';
 import type { World } from '../World';
@@ -136,7 +137,7 @@ function penetration(a: Entity, b: Entity, axis: PlaneAxis, dir: 1 | -1): number
 
 /** Whether `collider` belongs to `entity` or to something parented (at any depth) under it. */
 function travelsWith(collider: Entity, entity: Entity): boolean {
-  for (let e: Entity | null = collider; e; e = e.parent) if (e === entity) return true;
+  for (const e of parentChain(collider, (c) => c.parent)) if (e === entity) return true;
   return false;
 }
 
@@ -159,7 +160,7 @@ export function bodyOf(collider: Entity): Entity {
 }
 
 /** A collider stands for itself; any other entity stands for its direct collider children. */
-export function collidersOf(world: World, entity: Entity): Entity[] {
+function collidersOf(world: World, entity: Entity): Entity[] {
   if (entity.type === 'collider') return [entity];
   return world.childrenOf(entity).filter((e) => e.type === 'collider' && isHandleEnabled(e));
 }