feat: add a navigation picker after the breadcrumb's last segment

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/BreadcrumbNavPicker.svelte

@@ -0,0 +1,98 @@
+<!--
+@component
+The chevron after the breadcrumb's last segment: it opens the same picker a session's preview tab
+uses — the workspace pages, then the folders with their flows, scripts and apps — and picking a
+row navigates the app there.
+
+It lands where the page is: an item's folder with the item highlighted, or a page highlighted at
+the root, so moving to a sibling is one step rather than a drill from the top.
+-->
+<script lang="ts">
+	import { ChevronDown } from 'lucide-svelte'
+	import { goto } from '$app/navigation'
+	import Popover from '$lib/components/meltComponents/Popover.svelte'
+	import PreviewRouterPicker, { type Scope } from './sessions/PreviewRouterPicker.svelte'
+	import { pageKey, type PreviewTarget } from './sessions/previewRouter'
+	import { editPathFor, leafKeyFor, viewPathFor } from './workspacePicker'
+	import { base } from '$lib/base'
+	import type { PageHeaderItem } from './pageHeaderRegistry.svelte'
+
+	let {
+		item,
+		pagePath,
+		actingWorkspaceId,
+		iconSize = 14
+	}: {
+		/** The item the page is about, to land in its folder. */
+		item?: PageHeaderItem
+		/** The route of a workspace page, to highlight it among the pages. */
+		pagePath?: string
+		/** Load from, and navigate within, this workspace rather than the one the app points at. */
+		actingWorkspaceId?: string
+		iconSize?: number
+	} = $props()
+
+	let isOpen = $state(false)
+
+	// The tree files a path under its `f/<folder>` or `u/<user>` scope, then one branch per
+	// subfolder, each keyed by its full path — so the item's own folder is its path minus the name.
+	const initialScope = $derived.by<Scope>(() => {
+		const parts = item?.path?.split('/') ?? []
+		return parts.length >= 3 ? { kind: 'all', dir: parts.slice(0, -1).join('/') } : undefined
+	})
+	const initialHighlight = $derived(
+		item?.kind && item.path
+			? leafKeyFor(item.kind, item.path)
+			: pagePath
+				? pageKey(pagePath)
+				: undefined
+	)
+
+	// A page acting on another workspace than the app's (a session in a fork) keeps acting on it:
+	// the route reads `?workspace=` before the store.
+	function withWorkspace(href: string): string {
+		if (!actingWorkspaceId) return href
+		const sep = href.includes('?') ? '&' : '?'
+		return `${href}${sep}workspace=${encodeURIComponent(actingWorkspaceId)}`
+	}
+
+	function hrefFor(target: PreviewTarget): string | undefined {
+		if (target.type === 'page') return target.href
+		if (target.type === 'item') {
+			const path = target.mode === 'view' ? viewPathFor(target.item) : editPathFor(target.item)
+			return `${base}${path}`
+		}
+		return undefined
+	}
+
+	function pick(target: PreviewTarget) {
+		isOpen = false
+		const href = hrefFor(target)
+		if (href) goto(withWorkspace(href))
+	}
+</script>
+
+<Popover
+	placement="bottom-start"
+	usePointerDownOutside
+	excludeSelectors=".drawer"
+	disableFocusTrap
+	closeOnOtherPopoverOpen
+	bind:isOpen
+	openFocus="[data-workspace-picker-search]"
+	contentClasses="flex flex-col overflow-hidden"
+	class="shrink-0 flex items-center p-1.5 rounded text-tertiary hover:bg-surface-hover hover:text-primary transition-colors"
+	triggerAttrs={{ 'aria-label': 'Navigate to', title: 'Navigate to' }}
+>
+	{#snippet trigger()}
+		<ChevronDown size={iconSize} class="flex-shrink-0" />
+	{/snippet}
+	{#snippet content()}
+		<PreviewRouterPicker
+			{initialScope}
+			{initialHighlight}
+			workspaceId={actingWorkspaceId}
+			onPick={pick}
+		/>
+	{/snippet}
+</Popover>

frontend/src/lib/components/NavBreadcrumb.svelte

@@ -18,7 +18,7 @@ not this component) — so the lead can run the whole line.
 	import MeltButton from '$lib/components/meltComponents/MeltButton.svelte'
 	import BreadcrumbItemContent from './BreadcrumbItemContent.svelte'
 	import WorkspacePickerBody from '$lib/components/sidebar/WorkspacePickerBody.svelte'
-	import BreadcrumbSegment from '$lib/components/BreadcrumbSegment.svelte'
+	import BreadcrumbNavPicker from './BreadcrumbNavPicker.svelte'
 	import { userWorkspaces, workspaceStore, workspaceColor, superadmin } from '$lib/stores'
 	import { findWorkspaceRoot } from '$lib/utils/workspaceHierarchy'
 	import { useForkableWorkspaces } from '$lib/utils/useForkableWorkspaces.svelte'
@@ -31,7 +31,7 @@ not this component) — so the lead can run the whole line.
 	import { page } from '$app/state'
 	import { navPageFor } from './sidebar/navPages'
 	import { copyToClipboard, getContrastTextColor } from '$lib/utils'
-	import { KIND_LABEL_LOWER, kindKey } from '$lib/components/workspacePicker'
+	import { KIND_LABEL_LOWER } from '$lib/components/workspacePicker'
 	import type { PageHeaderItem, PageHeaderSection } from './pageHeaderRegistry.svelte'
 	import type { Snippet } from 'svelte'
 
@@ -236,6 +236,14 @@ not this component) — so the lead can run the whole line.
 	{/if}
 {/snippet}
 
+{#snippet navPicker()}
+	<!-- The page's own name is the last segment, so the chevron after it moves to a sibling page or
+	     item. Not in a session's preview band, which must not lead out of the host's workspace. -->
+	{#if !nameOnly}
+		<BreadcrumbNavPicker {item} pagePath={routePage?.path} {actingWorkspaceId} iconSize={ICON} />
+	{/if}
+{/snippet}
+
 {#snippet slash(extra = '')}
 	<!-- `extra` tops the workspace part's own 4px gap up to the 6px the breadcrumb puts around its
 	     other separators, so the slash before a fork is spaced like every other slash on the line. -->
@@ -307,10 +315,10 @@ not this component) — so the lead can run the whole line.
 						{/snippet}
 						{#snippet children({ item: menuItem })}
 							<WorkspacePickerBody
-									item={menuItem}
-									collapseFamilies={actingWorkspaceId != undefined}
-									closeMenu={() => workspaceMenu?.close()}
-								/>
+								item={menuItem}
+								collapseFamilies={actingWorkspaceId != undefined}
+								closeMenu={() => workspaceMenu?.close()}
+							/>
 						{/snippet}
 					</Menu>
 				{/snippet}
@@ -361,6 +369,7 @@ not this component) — so the lead can run the whole line.
 						{@render pathLabel()}
 					</button>
 				{/if}
+				{#if itemIsLast}{@render navPicker()}{/if}
 				{#if afterName}{@render afterName()}{/if}
 				{#if pathCopied}
 					<span
@@ -386,40 +395,47 @@ not this component) — so the lead can run the whole line.
 			</span>
 		{/if}
 	{:else if section?.kind}
-		<BreadcrumbSegment
-			label={KIND_LABEL_LOWER[section.kind]}
-			icon={sectionKindIcon}
-			extraClass={twMerge(SEGMENT, LAST)}
-			isCurrent
-			initialHighlight={kindKey(section.kind)}
-			initialScope={{ kind: section.kind }}
-			onPick={() => {}}
-		/>
+		<div class="flex items-center min-w-0">
+			<span
+				class={twMerge(SEGMENT, LAST, 'hover:bg-transparent hover:text-emphasis')}
+				aria-current="page"
+			>
+				{@render sectionKindIcon()}
+				<span class="truncate">{KIND_LABEL_LOWER[section.kind]}</span>
+			</span>
+			{@render navPicker()}
+		</div>
 	{:else if section}
 		<!-- A section's own widget lays out as a row: its title, and whatever belongs with it. -->
-		<span
-			class={twMerge(
-				SEGMENT,
-				LAST,
-				'hover:bg-transparent hover:text-emphasis',
-				section.content ? '' : 'truncate'
-			)}
-			aria-current="page"
-		>
-			{#if section.content}{@render section.content()}{:else}{section.label}{/if}
-		</span>
+		<div class="flex items-center min-w-0">
+			<span
+				class={twMerge(
+					SEGMENT,
+					LAST,
+					'hover:bg-transparent hover:text-emphasis',
+					section.content ? '' : 'truncate'
+				)}
+				aria-current="page"
+			>
+				{#if section.content}{@render section.content()}{:else}{section.label}{/if}
+			</span>
+			{@render navPicker()}
+		</div>
 		{#if afterName}{@render afterName()}{/if}
 	{:else if routePage}
 		{@const RouteIcon = routePage.icon}
 		<!-- shrink-0: a page's own name is short and is the one part of the trail worth keeping
 		     whole, so the workspace and fork names give way first when the bar is full. -->
-		<span
-			class={twMerge(SEGMENT, LAST, 'shrink-0 hover:bg-transparent hover:text-emphasis')}
-			aria-current="page"
-		>
-			{#if RouteIcon}<RouteIcon size={ICON} class="flex-shrink-0 text-tertiary" />{/if}
-			<span class="truncate">{routePage.label}</span>
-		</span>
+		<div class="flex items-center shrink-0">
+			<span
+				class={twMerge(SEGMENT, LAST, 'shrink-0 hover:bg-transparent hover:text-emphasis')}
+				aria-current="page"
+			>
+				{#if RouteIcon}<RouteIcon size={ICON} class="flex-shrink-0 text-tertiary" />{/if}
+				<span class="truncate">{routePage.label}</span>
+			</span>
+			{@render navPicker()}
+		</div>
 		{#if afterName}{@render afterName()}{/if}
 	{/if}
 </nav>

frontend/src/lib/components/PageHeaderBar.svelte

@@ -12,6 +12,7 @@ The row's height matches the sidebar's own header row, so the two read as one ba
 	import { navDetached } from './sidebar/navDetached.svelte'
 	import { navHandleSlot } from './sidebar/navHandlePlacement.svelte'
 	import NavBreadcrumb from './NavBreadcrumb.svelte'
+	import BreadcrumbNavPicker from './BreadcrumbNavPicker.svelte'
 	import { BAR_HEIGHT, pageHeader, PHONE_BAR } from './pageHeaderRegistry.svelte'
 	import ContextBridge from './ContextBridge.svelte'
 	import { afterNavigate } from '$app/navigation'
@@ -179,6 +180,10 @@ The row's height matches the sidebar's own header row, so the two read as one ba
 			{:else}
 				<span class="min-w-0 truncate text-xs font-medium text-emphasis">{item.summary}</span>
 			{/if}
+			<!-- The summary ends the trail here, so the breadcrumb's chevron follows it instead. -->
+			{#if !navHidden}
+				<BreadcrumbNavPicker {item} actingWorkspaceId={content?.actingWorkspaceId} />
+			{/if}
 		</div>
 	{/if}