feat(core): Add support for building LLM applications (#7235)

This extracts all core and editor changes from #7246 and #7137, so that
we can get these changes merged first.

ADO-1120

[DB Tests](https://github.com/n8n-io/n8n/actions/runs/6379749011)
[E2E Tests](https://github.com/n8n-io/n8n/actions/runs/6379751480)
[Workflow Tests](https://github.com/n8n-io/n8n/actions/runs/6379752828)

---------

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>
Co-authored-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Alex Grozav <alex@grozav.com>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/editor-ui/src/stores/ndv.store.ts

@@ -8,6 +8,7 @@ import type {
 	XYPosition,
 } from '@/Interface';
 import type { INodeIssues, IRunData } from 'n8n-workflow';
+import { NodeConnectionType } from 'n8n-workflow';
 import { defineStore } from 'pinia';
 import { v4 as uuid } from 'uuid';
 import { useWorkflowsStore } from './workflows.store';
@@ -124,7 +125,7 @@ export const useNDVStore = defineStore(STORES.NDV, {
 				return false;
 			}
 			const workflow = useWorkflowsStore().getCurrentWorkflow();
-			const parentNodes = workflow.getParentNodes(this.activeNode.name, 'main', 1);
+			const parentNodes = workflow.getParentNodes(this.activeNode.name, NodeConnectionType.Main, 1);
 			return parentNodes.includes(inputNodeName);
 		},
 		hoveringItemNumber(): number {
@@ -139,6 +140,9 @@ export const useNDVStore = defineStore(STORES.NDV, {
 		},
 	},
 	actions: {
+		setActiveNodeName(nodeName: string | null): void {
+			this.activeNodeName = nodeName;
+		},
 		setInputNodeName(nodeName: string | undefined): void {
 			this.input = {
 				...this.input,