Feat/stairs fence update (#226)

* feat: railing on the straight stairs and new fence

* feat: added spiral and curved stairs with bug fix for fence

* feat:fence are linked to each other ... so moving one move the other sharing the same coordinate

* fix: update stair railing logic to include front-side attachments for terminal landings

* Integrate fence rendering into the fence system

* fix: pass nodeId instead of undefined node to WallTreeNode and FenceTreeNode

TreeNode was passing `node` (undefined variable) instead of `nodeId` to
WallTreeNode and FenceTreeNode, causing a runtime ReferenceError.
Updated FenceTreeNode to accept nodeId and look up the node from the
scene store internally, consistent with all other tree node components.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: update fence icon with new isometric design

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Aymeric Rabot <aymeric@pascal.app>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/events/bus.ts

@@ -4,6 +4,7 @@ import type {
   BuildingNode,
   CeilingNode,
   DoorNode,
+  FenceNode,
   ItemNode,
   LevelNode,
   RoofNode,
@@ -41,6 +42,7 @@ export interface NodeEvent<T extends AnyNode = AnyNode> {
 }
 
 export type WallEvent = NodeEvent<WallNode>
+export type FenceEvent = NodeEvent<FenceNode>
 export type ItemEvent = NodeEvent<ItemNode>
 export type SiteEvent = NodeEvent<SiteNode>
 export type BuildingEvent = NodeEvent<BuildingNode>
@@ -111,6 +113,7 @@ type ThumbnailEvents = {
 
 type EditorEvents = GridEvents &
   NodeEvents<'wall', WallEvent> &
+  NodeEvents<'fence', FenceEvent> &
   NodeEvents<'item', ItemEvent> &
   NodeEvents<'site', SiteEvent> &
   NodeEvents<'building', BuildingEvent> &