feat: replace flow summary card with breadcrumb + frame the flow as a chat-owned card

- FlowBuilder: replace the SummaryPathDisplay box (path / summary stack)
  with an inline breadcrumb (Workflow icon + "Flows" / folder /
  summary-or-leaf, separated by ChevronRight). The breadcrumb derives
  $pathStore segments via $derived (breadcrumbParts/Folder/Leaf) so it
  can be referenced from the template without {@const}, which is not
  allowed as a direct child of <div>. Drops the now-unused
  SummaryPathDisplay import.
- design-sandbox: position the right pane as a contained "chat-owned"
  workspace — p-2 pl-0 padding plus an inner rounded-xl border / shadow-sm
  card wrapping FlowWrapper. Drop the left pane's right border so the
  chat reads as full-bleed primary content. Add a chat-side header
  (h-12 to match FlowBuilder's max-h-12 row) with a MessageSquare icon
  and a conversationTitle derived from the first user message in the
  current chat (truncated to 60 chars). Hide the splitpanes divider
  visually via a scoped :global(.design-sandbox-splitpanes ...) rule
  while keeping the hit area so the split is still resizable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/FlowBuilder.svelte

@@ -59,7 +59,9 @@
 		CheckCircle,
 		RefreshCw,
 		CheckCheck,
-		Disc
+		Disc,
+		ChevronRight,
+		Workflow
 	} from 'lucide-svelte'
 	import Awareness from './Awareness.svelte'
 	import { getAllModules } from './flows/flowExplorer'
@@ -71,7 +73,6 @@
 	import { resetAllTodos, skipAllTodos } from '$lib/tutorialUtils'
 	import { tutorialsToDo } from '$lib/stores'
 	import { getTutorialIndex } from '$lib/tutorials/config'
-	import SummaryPathDisplay from './SummaryPathDisplay.svelte'
 	import type { FlowBuilderWhitelabelCustomUi } from './custom_ui'
 	import FlowYamlEditor from './flows/header/FlowYamlEditor.svelte'
 	import { type TriggerContext, type ScheduleTrigger } from './triggers'
@@ -622,6 +623,15 @@
 	const flowEditorDrawer = writable<FlowEditorDrawer | undefined>(undefined)
 	const history = initHistory(untrack(() => flowStore).val)
 	const pathStore = writable<string>(untrack(() => pathStoreInit) ?? initialPath)
+
+	// Breadcrumb derivations for the flow header (replaces SummaryPathDisplay).
+	const breadcrumbParts = $derived(($pathStore ?? '').split('/').filter(Boolean))
+	const breadcrumbFolder = $derived(
+		breadcrumbParts.length > 1 ? breadcrumbParts.slice(0, -1).join('/') : ''
+	)
+	const breadcrumbLeaf = $derived(
+		breadcrumbParts.length > 0 ? breadcrumbParts[breadcrumbParts.length - 1] : 'untitled'
+	)
 	const captureOn = writable<boolean>(false)
 	const showCaptureHint = writable<boolean | undefined>(undefined)
 	const flowInputEditorStateStore = writable<FlowInputEditorState>({
@@ -1150,13 +1160,20 @@
 			<div
 				class="justify-between flex flex-row items-center pl-2 pr-4 space-x-4 scrollbar-hidden overflow-x-auto max-h-12 h-full relative"
 			>
-				<div class="flex w-full gap-8 items-center min-w-0">
-					<SummaryPathDisplay
-						bind:summary={flowStore.val.summary}
-						bind:path={$pathStore}
-						kind="flow"
-						editable
-					/>
+				<div class="flex w-full gap-1.5 items-center min-w-0 text-xs">
+					<Workflow class="w-3.5 h-3.5 text-secondary shrink-0" />
+					<span class="text-secondary shrink-0">Flows</span>
+					{#if breadcrumbFolder}
+						<ChevronRight class="w-3 h-3 text-secondary opacity-60 shrink-0" />
+						<span class="text-secondary truncate font-mono">{breadcrumbFolder}</span>
+					{/if}
+					<ChevronRight class="w-3 h-3 text-secondary opacity-60 shrink-0" />
+					<span
+						class="font-medium text-primary truncate"
+						title={flowStore.val.summary || breadcrumbLeaf}
+					>
+						{flowStore.val.summary || breadcrumbLeaf}
+					</span>
 				</div>
 
 				<div class="gap-4 flex-row hidden md:flex whitespace-nowrap">

frontend/src/routes/(root)/(logged)/design-sandbox/+page.svelte

@@ -14,6 +14,7 @@
 		previewModalState,
 		closePreviewModal
 	} from '$lib/components/copilot/chat/previewModalState.svelte'
+	import { MessageSquare } from 'lucide-svelte'
 
 	// Fake conversation: user asks the assistant to build a 3-step user-engagement flow.
 	const fakeMessages: DisplayMessage[] = [
@@ -203,23 +204,49 @@
 	let customUi: FlowBuilderWhitelabelCustomUi = {
 		aiAgent: true
 	}
+
+	// Conversation title shown in the chat topbar. Derived from the first user
+	// message in the current chat, truncated. Falls back to a placeholder while
+	// the chat is empty.
+	const conversationTitle = $derived.by(() => {
+		const firstUser = aiChatManager.displayMessages.find((m) => m.role === 'user')
+		if (!firstUser) return 'New conversation'
+		const text = firstUser.content.trim()
+		const truncated = text.length > 60 ? text.slice(0, 60).trimEnd() + '…' : text
+		return truncated
+	})
 </script>
 
 <div class="h-full w-full flex flex-col min-h-0">
-	<Splitpanes horizontal={false} class="flex-1 min-h-0">
-		<Pane size={50} minSize={20} class="flex flex-col min-h-0 border-r border-light">
-			<AIChat />
+	<Splitpanes horizontal={false} class="design-sandbox-splitpanes flex-1 min-h-0">
+		<Pane size={50} minSize={20} class="flex flex-col min-h-0">
+			<div class="flex flex-row items-center gap-2 px-3 h-12 bg-surface shrink-0">
+				<MessageSquare class="w-3.5 h-3.5 text-secondary shrink-0" />
+				<span class="text-xs font-medium text-primary truncate" title={conversationTitle}>
+					{conversationTitle}
+				</span>
+			</div>
+			<div class="flex-1 min-h-0">
+				<AIChat />
+			</div>
 		</Pane>
-		<Pane size={50} minSize={30} class="flex flex-col min-h-0">
-			<FlowWrapper
-				disableAi
-				pathStoreInit="u/admin/sandbox_flow"
-				{customUi}
-				selectedId={undefined}
-				newFlow
-				{flowStore}
-				{flowStateStore}
-			/>
+		<!-- The right pane is a contained, padded card to make it visually
+		     clear that the flow view "belongs to" the chat on the left rather
+		     than being its own root view. -->
+		<Pane size={50} minSize={30} class="flex flex-col min-h-0 p-2 pl-0">
+			<div
+				class="flex-1 min-h-0 rounded-xl border border-light bg-surface overflow-hidden shadow-sm"
+			>
+				<FlowWrapper
+					disableAi
+					pathStoreInit="u/admin/sandbox_flow"
+					{customUi}
+					selectedId={undefined}
+					newFlow
+					{flowStore}
+					{flowStateStore}
+				/>
+			</div>
 		</Pane>
 	</Splitpanes>
 </div>
@@ -245,3 +272,17 @@
 		<ScheduleEditorInner bind:this={scheduleEditor} useDrawer={false} />
 	</div>
 </Modal2>
+
+<style>
+	/* Hide the visible splitpanes divider while keeping the hit area so the
+	   panel is still resizable. Scoped to this page via the wrapper class. */
+	:global(.design-sandbox-splitpanes > .splitpanes__splitter) {
+		background-color: transparent !important;
+		background-image: none !important;
+		border: none !important;
+	}
+	:global(.design-sandbox-splitpanes > .splitpanes__splitter::before),
+	:global(.design-sandbox-splitpanes > .splitpanes__splitter::after) {
+		display: none !important;
+	}
+</style>