ui: added single line reasoning preview (#23601)

* webui: added single line reasoning preview.

* patch: reduce width slightly for the previewing section

* refactor: move formatter constants to the right file

* feat: reimplement reasoning preview with throttled dynamic per-line rendering

* chore: fix spacing

Co-authored-by: Aleksander Grygier <aleksander.grygier@gmail.com>

* chore: refactor to requested changes

* refactor: grouped by capture pattern instead of block-level + inline

* ui: fax interrupt state only trigger for 1st reasoning message

* chore: make reasoning preview respects showThoughtInProgress setting

* chore; newline at EOF

Co-authored-by: Aleksander Grygier <aleksander.grygier@gmail.com>

* fix: thread rawContent so collapsible content can handle compute preview

* patch: showThoughtInProgress accidentally blocks rawContent being passed

* chore: fix lint

* chore: change smoke test

---------

Co-authored-by: Aleksander Grygier <aleksander.grygier@gmail.com>

tools/ui/src/lib/components/app/chat/ChatMessages/ChatMessageAgenticContent.svelte

@@ -31,7 +31,8 @@
 		agenticPendingPermissionRequest,
 		agenticResolvePermission,
 		agenticPendingContinueRequest,
-		agenticResolveContinue
+		agenticResolveContinue,
+		agenticLastError
 	} from '$lib/stores/agentic.svelte';
 	import { config } from '$lib/stores/settings.svelte';
 
@@ -56,6 +57,10 @@
 	const showToolCallInProgress = $derived(config().showToolCallInProgress as boolean);
 	const showThoughtInProgress = $derived(config().showThoughtInProgress as boolean);
 
+	const hasReasoningError = $derived(
+		isLastAssistantMessage ? !!agenticLastError(message.convId) : false
+	);
+
 	let permissionDismissed = $state(false);
 
 	const pendingPermission = $derived(
@@ -293,11 +298,21 @@
 			</div>
 		</CollapsibleContentBlock>
 	{:else if section.type === AgenticSectionType.REASONING}
+		{@const reasoningSubtitle = section.wasInterrupted
+			? hasReasoningError
+				? 'Error'
+				: 'Cancelled'
+			: isStreaming
+				? ''
+				: undefined}
+
 		<CollapsibleContentBlock
 			open={isExpanded(index, section)}
 			class="my-2"
 			icon={Brain}
 			title="Reasoning"
+			subtitle={reasoningSubtitle}
+			rawContent={section.content}
 			onToggle={() => toggleExpanded(index, section)}
 		>
 			<div class="pt-3">
@@ -308,7 +323,7 @@
 		</CollapsibleContentBlock>
 	{:else if section.type === AgenticSectionType.REASONING_PENDING}
 		{@const reasoningTitle = isStreaming ? 'Reasoning...' : 'Reasoning'}
-		{@const reasoningSubtitle = isStreaming ? '' : 'incomplete'}
+		{@const reasoningSubtitle = isStreaming ? '' : hasReasoningError ? 'Error' : 'Cancelled'}
 
 		<CollapsibleContentBlock
 			open={isExpanded(index, section)}
@@ -316,6 +331,7 @@
 			icon={Brain}
 			title={reasoningTitle}
 			subtitle={reasoningSubtitle}
+			rawContent={section.content}
 			{isStreaming}
 			onToggle={() => toggleExpanded(index, section)}
 		>