[Refactor] Split NodeSlot out to separate files (#960)

Split files only; no code changes.  New files moved to `/node`.

src/node/NodeOutputSlot.ts

@@ -0,0 +1,47 @@
+import type { INodeInputSlot, INodeOutputSlot, OptionalProps } from "@/interfaces"
+import type { LinkId } from "@/LLink"
+
+import { LabelPosition } from "@/draw"
+import { LiteGraph } from "@/litegraph"
+import { type IDrawOptions, NodeSlot } from "@/node/NodeSlot"
+
+export class NodeOutputSlot extends NodeSlot implements INodeOutputSlot {
+  links: LinkId[] | null
+  _data?: unknown
+  slot_index?: number
+
+  get isWidgetInputSlot(): false {
+    return false
+  }
+
+  constructor(slot: OptionalProps<INodeOutputSlot, "boundingRect">) {
+    super(slot)
+    this.links = slot.links
+    this._data = slot._data
+    this.slot_index = slot.slot_index
+  }
+
+  override isValidTarget(fromSlot: INodeInputSlot | INodeOutputSlot): boolean {
+    return "link" in fromSlot && LiteGraph.isValidConnection(this.type, fromSlot.type)
+  }
+
+  override isConnected(): boolean {
+    return this.links != null && this.links.length > 0
+  }
+
+  override draw(ctx: CanvasRenderingContext2D, options: Omit<IDrawOptions, "doStroke" | "labelPosition">) {
+    const originalTextAlign = ctx.textAlign
+    const originalStrokeStyle = ctx.strokeStyle
+    ctx.textAlign = "right"
+    ctx.strokeStyle = "black"
+
+    super.draw(ctx, {
+      ...options,
+      labelPosition: LabelPosition.Left,
+      doStroke: true,
+    })
+
+    ctx.textAlign = originalTextAlign
+    ctx.strokeStyle = originalStrokeStyle
+  }
+}