feat(manacore/web): clickable cross-module links with overlay stacking

Clicking a linked item in a DetailView opens the target app's DetailView
as a stacked overlay on top of the current one. Supports:
- Cross-app navigation (e.g. click linked event from todo detail)
- Back button to return to previous overlay
- Correct app color + title in overlay header
- Overlay stack with goBack() popping the top frame
- Added paramKey to EntityDescriptor for correct ID mapping

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/manacore/apps/web/src/lib/components/links/LinkedItems.svelte

@@ -1,6 +1,6 @@
 <!--
   LinkedItems — Shows cross-module links for a record.
-  Displays linked items as clickable pills with app color and cached title.
+  Clicking a link opens the target item's DetailView as a cross-detail overlay.
 -->
 <script lang="ts">
 	import {
@@ -9,16 +9,24 @@
 		type LocalManaLink,
 	} from '@manacore/shared-links';
 	import { getAppEntry } from '$lib/components/workbench/app-registry';
-	import { ArrowSquareOut } from '@manacore/shared-icons';
+	import type { ViewProps } from '$lib/components/workbench/nav-stack';
 
 	interface Props {
 		recordRef: ManaRecordRef;
+		navigate: ViewProps['navigate'];
 	}
 
-	let { recordRef }: Props = $props();
+	let { recordRef, navigate }: Props = $props();
 
 	const linksQuery = useLinksForRecord(recordRef);
 	let links = $derived(linksQuery.value ?? []);
+
+	function openLink(link: LocalManaLink) {
+		navigate('cross-detail', {
+			_targetApp: link.targetApp,
+			_targetId: link.targetId,
+		});
+	}
 </script>
 
 {#if links.length > 0}
@@ -28,7 +36,7 @@
 			{#each links as link (link.id)}
 				{@const appEntry = getAppEntry(link.targetApp)}
 				{@const color = link.cachedTarget?.color ?? appEntry?.color ?? '#6B7280'}
-				<div class="link-item">
+				<button class="link-item" onclick={() => openLink(link)}>
 					<span class="link-dot" style="background: {color}"></span>
 					<div class="link-content">
 						<span class="link-title">{link.cachedTarget?.title ?? link.targetId}</span>
@@ -37,7 +45,7 @@
 						{/if}
 					</div>
 					<span class="link-app">{link.cachedTarget?.appName ?? link.targetApp}</span>
-				</div>
+				</button>
 			{/each}
 		</div>
 	</div>
@@ -69,17 +77,19 @@
 		border-radius: 0.375rem;
 		background: rgba(0, 0, 0, 0.02);
 		border: 1px solid rgba(0, 0, 0, 0.04);
+		cursor: pointer;
+		text-align: left;
 		transition: background 0.15s;
 	}
 	.link-item:hover {
-		background: rgba(0, 0, 0, 0.04);
+		background: rgba(0, 0, 0, 0.05);
 	}
 	:global(.dark) .link-item {
 		background: rgba(255, 255, 255, 0.02);
 		border-color: rgba(255, 255, 255, 0.04);
 	}
 	:global(.dark) .link-item:hover {
-		background: rgba(255, 255, 255, 0.05);
+		background: rgba(255, 255, 255, 0.06);
 	}
 	.link-dot {
 		width: 8px;

apps/manacore/apps/web/src/lib/components/workbench/AppPage.svelte

@@ -4,7 +4,7 @@
   that floats slightly larger than the panel underneath.
 -->
 <script lang="ts">
-	import { X, CaretUp, CaretDown, SpinnerGap } from '@manacore/shared-icons';
+	import { X, CaretUp, CaretDown, ArrowLeft, SpinnerGap } from '@manacore/shared-icons';
 	import { PageShell } from '$lib/components/page-carousel';
 	import { getAppEntry } from './app-registry';
 	import type { Component } from 'svelte';
@@ -76,23 +76,28 @@
 		}
 	});
 
-	// ── Overlay ─────────────────────────────────────────────
+	// ── Overlay Stack ───────────────────────────────────────
 	interface OverlayFrame {
 		viewName: string;
 		params: Record<string, unknown>;
 		component: Component | null;
+		/** App color for the overlay header (for cross-detail). */
+		overlayColor?: string;
+		/** App name for the overlay header (for cross-detail). */
+		overlayTitle?: string;
 	}
 
-	let overlay = $state<OverlayFrame | null>(null);
-	let hasOverlay = $derived(overlay !== null);
+	let overlayStack = $state<OverlayFrame[]>([]);
+	let overlay = $derived(overlayStack.length > 0 ? overlayStack[overlayStack.length - 1] : null);
+	let hasOverlay = $derived(overlayStack.length > 0);
 
-	// Sibling item IDs for prev/next navigation
+	// Sibling item IDs for prev/next navigation (only for first overlay level)
 	let siblingIds = $state<string[]>([]);
 	let siblingKey = $state<string>('');
 	let cachedOverlayComponent = $state<Component | null>(null);
 
 	let currentSiblingIndex = $derived(() => {
-		if (!overlay || !siblingKey || siblingIds.length === 0) return -1;
+		if (!overlay || !siblingKey || siblingIds.length === 0 || overlayStack.length > 1) return -1;
 		const currentId = overlay.params[siblingKey] as string;
 		return siblingIds.indexOf(currentId);
 	});
@@ -103,9 +108,42 @@
 
 	function navigate(viewName: string, params: Record<string, unknown> = {}) {
 		if (viewName === 'list') {
-			overlay = null;
+			overlayStack = [];
+			siblingIds = [];
+			siblingKey = '';
 			return;
 		}
+
+		// Cross-detail: open a detail view from another app
+		if (viewName === 'cross-detail') {
+			const targetApp = params._targetApp as string;
+			const targetId = params._targetId as string;
+			if (!targetApp || !targetId) return;
+
+			const targetEntity = getEntity(targetApp);
+			const targetAppEntry = getAppEntry(targetApp);
+			const targetViewEntry = targetAppEntry?.views?.detail;
+			if (!targetViewEntry || !targetEntity) {
+				console.warn(`No detail view registered for app "${targetApp}"`);
+				return;
+			}
+
+			targetViewEntry.load().then((mod) => {
+				overlayStack = [
+					...overlayStack,
+					{
+						viewName: 'cross-detail',
+						params: { [targetEntity.paramKey]: targetId },
+						component: mod.default,
+						overlayColor: targetAppEntry?.color,
+						overlayTitle: targetAppEntry?.name,
+					},
+				];
+			});
+			return;
+		}
+
+		// Normal detail view within the same app
 		const viewEntry = appEntry?.views?.[viewName];
 		if (!viewEntry) {
 			console.warn(`View "${viewName}" not registered for app "${appId}"`);
@@ -117,7 +155,7 @@
 		if (ids && key) {
 			siblingIds = ids;
 			siblingKey = key;
-		} else if (!overlay) {
+		} else if (overlayStack.length === 0) {
 			siblingIds = [];
 			siblingKey = '';
 		}
@@ -128,24 +166,32 @@
 
 		viewEntry.load().then((mod) => {
 			cachedOverlayComponent = mod.default;
-			overlay = { viewName, params: viewParams, component: mod.default };
+			// Replace the stack (not push) for same-app detail navigation
+			overlayStack = [{ viewName, params: viewParams, component: mod.default }];
 		});
 	}
 
 	function goBack() {
-		overlay = null;
-		siblingIds = [];
-		siblingKey = '';
+		if (overlayStack.length > 1) {
+			// Pop the top overlay (cross-detail)
+			overlayStack = overlayStack.slice(0, -1);
+		} else {
+			overlayStack = [];
+			siblingIds = [];
+			siblingKey = '';
+		}
 	}
 
 	function goToPrev() {
 		const idx = currentSiblingIndex();
-		if (idx > 0 && overlay && siblingKey && cachedOverlayComponent) {
-			overlay = {
-				viewName: overlay.viewName,
-				params: { ...overlay.params, [siblingKey]: siblingIds[idx - 1] },
-				component: cachedOverlayComponent,
-			};
+		if (idx > 0 && overlay && siblingKey && cachedOverlayComponent && overlayStack.length === 1) {
+			overlayStack = [
+				{
+					viewName: overlay.viewName,
+					params: { ...overlay.params, [siblingKey]: siblingIds[idx - 1] },
+					component: cachedOverlayComponent,
+				},
+			];
 		}
 	}
 
@@ -156,13 +202,16 @@
 			idx < siblingIds.length - 1 &&
 			overlay &&
 			siblingKey &&
-			cachedOverlayComponent
+			cachedOverlayComponent &&
+			overlayStack.length === 1
 		) {
-			overlay = {
-				viewName: overlay.viewName,
-				params: { ...overlay.params, [siblingKey]: siblingIds[idx + 1] },
-				component: cachedOverlayComponent,
-			};
+			overlayStack = [
+				{
+					viewName: overlay.viewName,
+					params: { ...overlay.params, [siblingKey]: siblingIds[idx + 1] },
+					component: cachedOverlayComponent,
+				},
+			];
 		}
 	}
 
@@ -173,7 +222,7 @@
 		if (!overlay) return;
 		function handleGlobalClick(e: MouseEvent) {
 			if (overlayCardEl && !overlayCardEl.contains(e.target as Node)) {
-				overlay = null;
+				overlayStack = [];
 				siblingIds = [];
 				siblingKey = '';
 			}
@@ -239,14 +288,28 @@
 
 				<!-- Header -->
 				<div class="overlay-header">
-					<span class="color-dot" style="background-color: {appColor}"></span>
-					<span class="overlay-title">{appName}</span>
-					{#if siblingIds.length > 1}
+					{#if overlayStack.length > 1}
+						<button class="back-btn" onclick={goBack} title="Zurück">
+							<ArrowLeft size={12} />
+						</button>
+					{/if}
+					<span class="color-dot" style="background-color: {overlay.overlayColor ?? appColor}"
+					></span>
+					<span class="overlay-title">{overlay.overlayTitle ?? appName}</span>
+					{#if siblingIds.length > 1 && overlayStack.length === 1}
 						<span class="nav-counter">
 							{currentSiblingIndex() + 1}/{siblingIds.length}
 						</span>
 					{/if}
-					<button class="close-btn" onclick={goBack} title="Schließen">
+					<button
+						class="close-btn"
+						onclick={() => {
+							overlayStack = [];
+							siblingIds = [];
+							siblingKey = '';
+						}}
+						title="Schließen"
+					>
 						<X size={14} />
 					</button>
 				</div>
@@ -402,6 +465,28 @@
 		color: #f3f4f6;
 	}
 
+	.back-btn {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		width: 20px;
+		height: 20px;
+		border-radius: 0.25rem;
+		border: none;
+		background: transparent;
+		color: #9ca3af;
+		cursor: pointer;
+		transition: all 0.15s;
+	}
+	.back-btn:hover {
+		background: rgba(0, 0, 0, 0.06);
+		color: #374151;
+	}
+	:global(.dark) .back-btn:hover {
+		background: rgba(255, 255, 255, 0.1);
+		color: #f3f4f6;
+	}
+
 	.close-btn {
 		display: flex;
 		align-items: center;

apps/manacore/apps/web/src/lib/entities/types.ts

@@ -16,6 +16,9 @@ export interface EntityDescriptor {
 	appId: string;
 	collection: string;
 
+	/** Param key name used in DetailView (e.g. 'taskId', 'eventId', 'contactId'). */
+	paramKey: string;
+
 	/** How to display an item in link previews and drag ghosts. */
 	getDisplayData: (item: Record<string, unknown>) => EntityDisplayData;
 

apps/manacore/apps/web/src/lib/modules/calendar/entity.ts

@@ -6,6 +6,7 @@ import type { EntityDescriptor } from '$lib/entities/types';
 const calendarEntity: EntityDescriptor = {
 	appId: 'calendar',
 	collection: 'events',
+	paramKey: 'eventId',
 
 	getDisplayData: (item) => ({
 		title: (item.title as string) || 'Termin',

apps/manacore/apps/web/src/lib/modules/calendar/views/DetailView.svelte

@@ -180,7 +180,7 @@
 		{/if}
 
 		<!-- Links -->
-		<LinkedItems recordRef={{ app: 'calendar', collection: 'events', id: eventId }} />
+		<LinkedItems recordRef={{ app: 'calendar', collection: 'events', id: eventId }} {navigate} />
 
 		<!-- Description -->
 		<div class="section">

apps/manacore/apps/web/src/lib/modules/contacts/entity.ts

@@ -4,6 +4,7 @@ import type { EntityDescriptor } from '$lib/entities/types';
 const contactsEntity: EntityDescriptor = {
 	appId: 'contacts',
 	collection: 'contacts',
+	paramKey: 'contactId',
 
 	getDisplayData: (item) => {
 		const name = [item.firstName, item.lastName].filter(Boolean).join(' ');

apps/manacore/apps/web/src/lib/modules/contacts/views/DetailView.svelte

@@ -291,7 +291,10 @@
 		{/if}
 
 		<!-- Links -->
-		<LinkedItems recordRef={{ app: 'contacts', collection: 'contacts', id: contactId }} />
+		<LinkedItems
+			recordRef={{ app: 'contacts', collection: 'contacts', id: contactId }}
+			{navigate}
+		/>
 
 		<!-- Notes -->
 		<div class="section">

apps/manacore/apps/web/src/lib/modules/todo/entity.ts

@@ -5,6 +5,7 @@ import type { EntityDescriptor } from '$lib/entities/types';
 const todoEntity: EntityDescriptor = {
 	appId: 'todo',
 	collection: 'tasks',
+	paramKey: 'taskId',
 
 	getDisplayData: (item) => ({
 		title: (item.title as string) || 'Aufgabe',

apps/manacore/apps/web/src/lib/modules/todo/views/DetailView.svelte

@@ -192,7 +192,7 @@
 		{/if}
 
 		<!-- Links -->
-		<LinkedItems recordRef={{ app: 'todo', collection: 'tasks', id: taskId }} />
+		<LinkedItems recordRef={{ app: 'todo', collection: 'tasks', id: taskId }} {navigate} />
 
 		<!-- Description -->
 		<div class="section">