feat: AI nodes usability fixes + Summarization Chain V2 (#7949)

Fixes:
- Refactor connection snapping when dragging and enable it also for
non-main connection types
- Fix propagation of errors from sub-nodes
- Fix chat scrolling when sending/receiving messages
- Prevent empty chat messages
- Fix sub-node selected styles
- Fix output names text overflow

Usability improvements:
- Auto-add manual chat trigger for agents & chain nodes
- Various labels and description updates
- Make the output parser input optional for Basic LLM Chain
- Summarization Chain V2 with a simplified document loader & text
chunking mode

#### How to test the change:
Example workflow showcasing different operation mode of the new
summarization chain:

[Summarization_V2.json](https://github.com/n8n-io/n8n/files/13599901/Summarization_V2.json)


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers
-
https://www.notion.so/n8n/David-Langchain-Posthog-notes-7a9294938420403095f4508f1a21d31d
- https://linear.app/n8n/issue/N8N-7070/ux-fixes-batch
- https://linear.app/n8n/issue/N8N-7071/ai-sub-node-bugs


## Review / Merge checklist
- [x] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [x] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
> *(internal)* You can use Slack commands to trigger [e2e
tests](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#a39f9e5ba64a48b58a71d81c837e8227)
or [deploy test
instance](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#f6a177d32bde4b57ae2da0b8e454bfce)
or [deploy early access version on
Cloud](https://www.notion.so/n8n/Cloudbot-3dbe779836004972b7057bc989526998?pvs=4#fef2d36ab02247e1a0f65a74f6fb534e).

---------

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Elias Meire <elias@meire.dev>

packages/editor-ui/src/components/Node/NodeCreator/ItemTypes/ViewItem.vue

@@ -2,6 +2,7 @@
 	<n8n-node-creator-node
 		:class="$style.view"
 		:title="view.title"
+		:tag="view.tag"
 		:isTrigger="false"
 		:description="view.description"
 		:showActionArrow="true"

packages/editor-ui/src/components/Node/NodeCreator/composables/useActions.ts

@@ -10,9 +10,14 @@ import type {
 	LabelCreateElement,
 } from '@/Interface';
 import {
+	AGENT_NODE_TYPE,
+	BASIC_CHAIN_NODE_TYPE,
+	MANUAL_CHAT_TRIGGER_NODE_TYPE,
 	MANUAL_TRIGGER_NODE_TYPE,
 	NODE_CREATOR_OPEN_SOURCES,
 	NO_OP_NODE_TYPE,
+	OPEN_AI_ASSISTANT_NODE_TYPE,
+	QA_CHAIN_NODE_TYPE,
 	SCHEDULE_TRIGGER_NODE_TYPE,
 	SPLIT_IN_BATCHES_NODE_TYPE,
 	STICKY_NODE_TYPE,
@@ -34,6 +39,12 @@ export const useActions = () => {
 	const nodeCreatorStore = useNodeCreatorStore();
 	const instance = getCurrentInstance();
 
+	const singleNodeOpenSources = [
+		NODE_CREATOR_OPEN_SOURCES.PLUS_ENDPOINT,
+		NODE_CREATOR_OPEN_SOURCES.NODE_CONNECTION_ACTION,
+		NODE_CREATOR_OPEN_SOURCES.NODE_CONNECTION_DROP,
+	];
+
 	const actionsCategoryLocales = computed(() => {
 		return {
 			actions: instance?.proxy.$locale.baseText('nodeCreator.actionsCategory.actions') ?? '',
@@ -156,11 +167,6 @@ export const useActions = () => {
 		const workflowContainsTrigger = workflowTriggerNodes.length > 0;
 		const isTriggerPanel = selectedView === TRIGGER_NODE_CREATOR_VIEW;
 		const onlyStickyNodes = addedNodes.every((node) => node.type === STICKY_NODE_TYPE);
-		const singleNodeOpenSources = [
-			NODE_CREATOR_OPEN_SOURCES.PLUS_ENDPOINT,
-			NODE_CREATOR_OPEN_SOURCES.NODE_CONNECTION_ACTION,
-			NODE_CREATOR_OPEN_SOURCES.NODE_CONNECTION_DROP,
-		];
 
 		// If the node creator was opened from the plus endpoint, node connection action, or node connection drop
 		// then we do not want to append the manual trigger
@@ -173,6 +179,22 @@ export const useActions = () => {
 			!onlyStickyNodes
 		);
 	}
+	function shouldPrependChatTrigger(addedNodes: AddedNode[]): boolean {
+		const { allNodes } = useWorkflowsStore();
+
+		const COMPATIBLE_CHAT_NODES = [
+			QA_CHAIN_NODE_TYPE,
+			AGENT_NODE_TYPE,
+			BASIC_CHAIN_NODE_TYPE,
+			OPEN_AI_ASSISTANT_NODE_TYPE,
+		];
+
+		const isChatTriggerMissing =
+			allNodes.find((node) => node.type === MANUAL_CHAT_TRIGGER_NODE_TYPE) === undefined;
+		const isCompatibleNode = addedNodes.some((node) => COMPATIBLE_CHAT_NODES.includes(node.type));
+
+		return isCompatibleNode && isChatTriggerMissing;
+	}
 
 	function getAddedNodesAndConnections(addedNodes: AddedNode[]): AddedNodesAndConnections {
 		if (addedNodes.length === 0) {
@@ -188,7 +210,13 @@ export const useActions = () => {
 			nodeToAutoOpen.openDetail = true;
 		}
 
-		if (shouldPrependManualTrigger(addedNodes)) {
+		if (shouldPrependChatTrigger(addedNodes)) {
+			addedNodes.unshift({ type: MANUAL_CHAT_TRIGGER_NODE_TYPE, isAutoAdd: true });
+			connections.push({
+				from: { nodeIndex: 0 },
+				to: { nodeIndex: 1 },
+			});
+		} else if (shouldPrependManualTrigger(addedNodes)) {
 			addedNodes.unshift({ type: MANUAL_TRIGGER_NODE_TYPE, isAutoAdd: true });
 			connections.push({
 				from: { nodeIndex: 0 },

packages/editor-ui/src/components/Node/NodeCreator/viewsData.ts

@@ -76,6 +76,7 @@ export interface NodeViewItem {
 		group?: string[];
 		sections?: NodeViewItemSection[];
 		description?: string;
+		tag?: string;
 		forceIncludeNodes?: string[];
 	};
 	category?: string | string[];
@@ -451,6 +452,7 @@ export function RegularView(nodes: SimplifiedNodeType[]) {
 				title: i18n.baseText('nodeCreator.aiPanel.langchainAiNodes'),
 				icon: 'robot',
 				description: i18n.baseText('nodeCreator.aiPanel.nodesForAi'),
+				tag: i18n.baseText('nodeCreator.aiPanel.newTag'),
 			},
 		});