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/@n8n/nodes-langchain/nodes/document_loaders/DocumentBinaryInputLoader/DocumentBinaryInputLoader.node.ts

@@ -17,6 +17,7 @@ import { getConnectionHintNoticeField, metadataFilterField } from '../../../util
 import 'mammoth'; // for docx
 import 'epub2'; // for epub
 import 'pdf-parse'; // for pdf
+import type { TextSplitter } from 'langchain/text_splitter';
 
 export class DocumentBinaryInputLoader implements INodeType {
 	description: INodeTypeDescription = {
@@ -177,7 +178,13 @@ export class DocumentBinaryInputLoader implements INodeType {
 
 	async supplyData(this: IExecuteFunctions): Promise<SupplyData> {
 		this.logger.verbose('Supply Data for Binary Input Loader');
-		const processor = new N8nBinaryLoader(this);
+		const textSplitter = (await this.getInputConnectionData(
+			NodeConnectionType.AiTextSplitter,
+			0,
+		)) as TextSplitter | undefined;
+
+		const binaryDataKey = this.getNodeParameter('binaryDataKey', 0) as string;
+		const processor = new N8nBinaryLoader(this, undefined, binaryDataKey, textSplitter);
 
 		return {
 			response: logWrapper(processor, this),