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/design-system/src/components/N8nNodeCreatorNode/NodeCreatorNode.vue

@@ -2,12 +2,14 @@
 import { useI18n } from '@/composables/useI18n';
 import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome';
 import N8nTooltip from '../N8nTooltip';
+import { ElTag } from 'element-plus';
 
 export interface Props {
 	active?: boolean;
 	isAi?: boolean;
 	isTrigger?: boolean;
 	description?: string;
+	tag?: string;
 	title: string;
 	showActionArrow?: boolean;
 }
@@ -35,6 +37,9 @@ const i18n = useI18n();
 		<div>
 			<div :class="$style.details">
 				<span :class="$style.name" v-text="title" data-test-id="node-creator-item-name" />
+				<el-tag v-if="tag" :class="$style.tag" size="small" round type="success">
+					{{ tag }}
+				</el-tag>
 				<font-awesome-icon
 					icon="bolt"
 					v-if="isTrigger"
@@ -82,7 +87,9 @@ const i18n = useI18n();
 .creatorNode:hover .panelIcon {
 	color: var(--action-arrow-color-hover, var(--color-text-light));
 }
-
+.tag {
+	margin-left: var(--spacing-2xs);
+}
 .panelIcon {
 	flex-grow: 1;
 	display: flex;