**Fix smash items knocking kids out by excluding kidCategory from collision mask**

The previous fix only exempted the bus's `busCategory` from smashed item collisions, leaving items still colliding with and ejecting kids riding at the open top of the compartment. This commit:

- Adds `~this.bus.kidCategory` to the initial collision filter in `_buildItem`, so new smash items are ghost-to-kids from creation
- Updates the post-smash mask update to also clear `kidCategory` (previously only `busCategory` was cleared), preventing a regression where item↔kid collisions would silently re-enable after the smash animation

Items remain solid against terrain and other props, preserving normal landing/physics behavior while ensuring their impact can no longer contribute to ejecting kids.

src/entities/SmashItemManager.js

@@ -67,6 +67,15 @@ export default class SmashItemManager {
       friction: SMASH_ITEM.friction,
       frictionAir: SMASH_ITEM.frictionAir,
       restitution: SMASH_ITEM.restitution,
+      // Never collide with the bus's kids. Kids ride at the open top of the
+      // compartment, so an item slamming into the bus (or a smashed item
+      // launched up-and-forward) could otherwise knock them out. Clearing the
+      // dedicated kidCategory (not the default category, which terrain also
+      // uses) keeps the item solid against the bus (for the smash) and the
+      // terrain (so it lands) while making it a pure ghost to the kids -
+      // its impact can no longer contribute to ejecting them. (setStatic/
+      // setVelocity etc. are untouched; see the rest of this file.)
+      collisionFilter: { mask: 0xffffffff & ~this.bus.kidCategory },
     });
     image.setDisplaySize(SMASH_ITEM.displaySize, SMASH_ITEM.displaySize);
     image.setDepth(1); // same layer as the kids - over the ground, under the bus
@@ -125,10 +134,13 @@ export default class SmashItemManager {
     // see the vendored build). Set on the raw matter body directly: that's the
     // exact field canCollide reads, and matter-js recomputes pairs every step,
     // so this takes effect on the very next physics step. The item keeps its
-    // mask against everything ELSE (terrain, other items, kids), so it still
+    // mask against everything ELSE (terrain, other items) so it still lands
-    // lands and rests where it flies - only the bus is exempted. This is what
+    // and rests where it flies - the bus and the kids are exempted. This is
-    // makes the bus "drive through" a smashed prop instead of bumping it.
+    // what makes the bus "drive through" a smashed prop instead of bumping
-    image.body.collisionFilter.mask = 0xffffffff & ~this.bus.busCategory;
+    // it. Keep the kid exemption too (see _buildItem): clearing only
+    // busCategory here would silently re-enable item<->kid collisions after
+    // the smash.
+    image.body.collisionFilter.mask = 0xffffffff & ~this.bus.busCategory & ~this.bus.kidCategory;
 
     // setStatic(false) (Phaser component, same as in _buildItem) restores
     // the body's saved real mass/inertia - matter-js stashed them when the