feat: HVAC ductwork + DWV plumbing systems (#402)

Adds two new MEP node families (HVAC ductwork, DWV plumbing) built on a shared port-connectivity model. Co-authored by @sudhir9297.

packages/core/src/events/bus.ts

@@ -11,13 +11,22 @@ import type {
   DoorNode,
   DormerNode,
   DownspoutNode,
+  DuctFittingNode,
+  DuctSegmentNode,
+  DuctTerminalNode,
   ElevatorNode,
   EyebrowVentNode,
   FenceNode,
   GuideNode,
   GutterNode,
+  HvacEquipmentNode,
   ItemNode,
   LevelNode,
+  LinesetNode,
+  LiquidLineNode,
+  PipeFittingNode,
+  PipeSegmentNode,
+  PipeTrapNode,
   RidgeVentNode,
   RoofNode,
   RoofSegmentNode,
@@ -107,6 +116,15 @@ export type SolarPanelEvent = NodeEvent<SolarPanelNode>
 export type SkylightEvent = NodeEvent<SkylightNode>
 export type DormerEvent = NodeEvent<DormerNode>
 export type DownspoutEvent = NodeEvent<DownspoutNode>
+export type DuctSegmentEvent = NodeEvent<DuctSegmentNode>
+export type DuctFittingEvent = NodeEvent<DuctFittingNode>
+export type DuctTerminalEvent = NodeEvent<DuctTerminalNode>
+export type HvacEquipmentEvent = NodeEvent<HvacEquipmentNode>
+export type PipeSegmentEvent = NodeEvent<PipeSegmentNode>
+export type PipeFittingEvent = NodeEvent<PipeFittingNode>
+export type PipeTrapEvent = NodeEvent<PipeTrapNode>
+export type LinesetEvent = NodeEvent<LinesetNode>
+export type LiquidLineEvent = NodeEvent<LiquidLineNode>
 
 // Event suffixes - exported for use in hooks
 export const eventSuffixes = [
@@ -261,6 +279,15 @@ type EditorEvents = GridEvents &
   NodeEvents<'skylight', SkylightEvent> &
   NodeEvents<'dormer', DormerEvent> &
   NodeEvents<'downspout', DownspoutEvent> &
+  NodeEvents<'duct-segment', DuctSegmentEvent> &
+  NodeEvents<'duct-fitting', DuctFittingEvent> &
+  NodeEvents<'duct-terminal', DuctTerminalEvent> &
+  NodeEvents<'hvac-equipment', HvacEquipmentEvent> &
+  NodeEvents<'pipe-segment', PipeSegmentEvent> &
+  NodeEvents<'pipe-fitting', PipeFittingEvent> &
+  NodeEvents<'pipe-trap', PipeTrapEvent> &
+  NodeEvents<'lineset', LinesetEvent> &
+  NodeEvents<'liquid-line', LiquidLineEvent> &
   CameraControlEvents &
   ToolEvents &
   GuideEvents &