webui: Improve Chat Messages initial scroll + auto-scroll logic + add lazy loading with transitions to content blocks (#20999)

* refactor: Always use agentic content renderer for Assistant Message

* feat: Improve initial scroll + auto-scroll logic + implement fade in action for content blocks

* chore: update webui build output

tools/server/webui/src/lib/components/app/content/MarkdownContent.svelte

@@ -36,6 +36,7 @@
 	import { createAutoScrollController } from '$lib/hooks/use-auto-scroll.svelte';
 	import type { DatabaseMessageExtra } from '$lib/types/database';
 	import { config } from '$lib/stores/settings.svelte';
+	import { fadeInView } from '$lib/actions/fade-in-view.svelte';
 
 	interface Props {
 		attachments?: DatabaseMessageExtra[];
@@ -598,7 +599,7 @@
 		: ''}"
 >
 	{#each renderedBlocks as block (block.id)}
-		<div class="markdown-block" data-block-id={block.id}>
+		<div class="markdown-block" data-block-id={block.id} use:fadeInView={{ skipIfVisible: true }}>
 			<!-- eslint-disable-next-line no-at-html-tags -->
 			{@html block.html}
 		</div>
@@ -651,7 +652,6 @@
 />
 
 <style>
-	.markdown-block,
 	.markdown-block--unstable {
 		display: contents;
 	}