feat(timeline): render a same-year curated event as its cluster card header

A curated event with letters in its own band now becomes the contained card header
(glyph, title, date, provenance, edit pencil) instead of a separate floating pill —
the title reads once. Derived life-events, world-bands, and letterless event pills
are unchanged (REQ-001 amended for curated-with-letters; the identity fixture now
links its letter to the curated event so the letterless world band stays a band).

Refs #827

frontend/src/lib/timeline/LetterBucket.svelte

@@ -3,18 +3,24 @@ import * as m from '$lib/paraglide/messages.js';
 import LetterCard from './LetterCard.svelte';
 import BucketHeaderChip from './BucketHeaderChip.svelte';
 import { entryKey } from './entryKey';
+import { getAccentConfig } from './eventCardConfig';
+import { timelineDateLabel } from './dateLabel';
 import { CLUSTER_PREVIEW, tagColorVar, type LetterBucket } from './timelineGrouping';
+import type { components } from '$lib/generated/api';
+
+type TimelineEntryDTO = components['schemas']['TimelineEntryDTO'];
 
 /**
  * One cluster of loose letters, bound together by a coloured left rail so the group reads as a
- * unit (#827). The axis-fixed event/world-band layers are rendered elsewhere — this is only the
+ * unit (#827). The axis-fixed world-band layer is rendered elsewhere — this is only the
  * loose-letter bundling.
  *
  * - Thema: a tinted root-tag header chip + a rail in the tag colour, over compact cards whose own
  *   tag chip is suppressed (REQ-004/015/017).
- * - Ereignis: rendered `nested` directly beneath its event pill — no header (the pill is the
+ * - Ereignis: a same-year curated `event` becomes the card header (glyph, title, date,
- *   header), a mint rail, `.lcard.ev` cards (REQ-003/014). The standalone "Weitere Briefe" /
+ *   provenance, edit pencil) so its title reads once — no separate floating pill (#827 redesign,
- *   "Ohne Thema" fallback keeps its label and a neutral rail (REQ-006/007).
+ *   REQ-001/014). A cross-year cluster keeps a plain text header. The standalone "Weitere Briefe"
+ *   / "Ohne Thema" fallback keeps its label and a neutral dashed rail (REQ-006/007).
  *
  * A cluster shows its first `CLUSTER_PREVIEW` letters, then a show-more toggle reveals the rest
  * instead of flooding the timeline with every card (#827 redesign).
@@ -27,13 +33,36 @@ let {
 	// time from the band heading). Kept in the prop contract for callers/tests.
 	// eslint-disable-next-line @typescript-eslint/no-unused-vars
 	year = 0,
-	nested = false
+	nested = false,
-}: { bucket: LetterBucket; mode: 'event' | 'thema'; year?: number; nested?: boolean } = $props();
+	event = undefined,
+	canWrite = false
+}: {
+	bucket: LetterBucket;
+	mode: 'event' | 'thema';
+	year?: number;
+	nested?: boolean;
+	/** The same-year curated event whose letters this card holds — renders as the header. */
+	event?: TimelineEntryDTO;
+	canWrite?: boolean;
+} = $props();
 
 const count = $derived(bucket.letters.length);
 const fallbackLabel = $derived(
 	mode === 'event' ? m.timeline_bucket_other_letters() : m.timeline_bucket_no_topic()
 );
+
+// Event-as-header (#827 redesign): a same-year curated event renders as this card's header,
+// mirroring EventPill — glyph + title + date · provenance + an edit pencil for a curator. The
+// title is never repeated as a separate floating pill.
+const accent = $derived(event ? getAccentConfig(event) : null);
+const eventDateLabel = $derived(
+	event ? timelineDateLabel(event.eventDate, event.precision, event.eventDateEnd) : null
+);
+const provenance = $derived(
+	event?.derived ? m.timeline_provenance_derived() : m.timeline_provenance_curated()
+);
+const eventSubtitle = $derived(eventDateLabel ? `${eventDateLabel} · ${provenance}` : provenance);
+const canEdit = $derived(canWrite && !!event && !event.derived && event.eventId != null);
 // The left rail binds the cluster: the tag colour in Thema, mint for an Ereignis cluster,
 // neutral for the fallback (and for a colourless/unknown tag token).
 const railColor = $derived(bucket.kind === 'tag' ? tagColorVar(bucket.color) : null);
@@ -65,6 +94,43 @@ let revealed = $state(bucket.kind !== 'fallback');
 	data-bucket-kind={bucket.kind}
 >
 	{#if !nested}
+		{#if event && accent}
+			<!-- A same-year curated event IS the card header — its title reads once here, never
+			     also as a floating pill (#827 redesign, REQ-001/014). Glyph is aria-hidden with an
+			     sr-only label sibling (REQ-018); the edit pencil mirrors EventPill's gate. -->
+			<header
+				data-testid="bucket-event-header"
+				class="flex items-center gap-2 border-b border-line bg-canvas px-3 py-2"
+			>
+				<span
+					class="flex h-7 w-7 shrink-0 items-center justify-center rounded-full {accent.accent ===
+					'curated'
+						? 'bg-brand-mint text-brand-navy'
+						: 'bg-brand-navy text-brand-mint'}"
+				>
+					<span aria-hidden="true">{accent.glyph}</span>
+					<span class="sr-only">{accent.label}</span>
+				</span>
+				<span class="min-w-0 text-left">
+					<span class="block font-serif text-sm font-bold whitespace-pre-line text-brand-navy"
+						>{event.title}</span
+					>
+					<span class="block font-sans text-xs text-ink-3">
+						{eventSubtitle} <span data-testid="bucket-count">· {count}</span>
+					</span>
+				</span>
+				{#if canEdit}
+					<a
+						data-testid="event-edit"
+						href="/zeitstrahl/events/{event.eventId}/edit"
+						class="ml-auto rounded-sm px-1 font-sans text-xs text-ink-3 hover:text-brand-navy focus:outline-none focus-visible:ring-2 focus-visible:ring-brand-navy"
+					>
+						<span aria-hidden="true">✎</span>
+						<span class="sr-only">{m.btn_edit()}</span>
+					</a>
+				{/if}
+			</header>
+		{:else}
 			<header
 				class="flex items-center gap-2 px-3 py-2"
 				class:bg-canvas={isEventCluster}
@@ -84,6 +150,7 @@ let revealed = $state(bucket.kind !== 'fallback');
 				<span data-testid="bucket-count" class="font-sans text-xs text-ink-3">· {count}</span>
 			</header>
 		{/if}
+	{/if}
 
 	<div class="px-3 py-2">
 		{#if !revealed}

frontend/src/lib/timeline/LetterBucket.svelte.spec.ts

@@ -178,3 +178,55 @@ describe('LetterBucket — card chrome (#827 redesign)', () => {
 		expect(card.className).toContain('bg-surface');
 	});
 });
+
+describe('LetterBucket — event-as-header (#827 redesign)', () => {
+	it('renders the curated event as the card header when given an `event` (no separate pill)', () => {
+		const event = makeEntry({
+			kind: 'EVENT',
+			type: 'PERSONAL',
+			derived: false,
+			eventId: 'e1',
+			title: 'Ein gewaltiger Stadtbrand',
+			eventDate: '1916-07-06',
+			senderName: '',
+			receiverName: '',
+			documentId: undefined
+		});
+		const bucket: Bucket = {
+			key: 'event:e1',
+			kind: 'event',
+			title: 'Ein gewaltiger Stadtbrand',
+			color: null,
+			letters: [makeEntry({ documentId: 'a', linkedEventId: 'e1' })]
+		};
+		render(LetterBucket, { bucket, mode: 'event', year: 1916, event, canWrite: true });
+		const header = document.querySelector('[data-testid="bucket-event-header"]') as HTMLElement;
+		expect(header.textContent).toContain('Ein gewaltiger Stadtbrand');
+		expect(header.textContent).toContain(m.timeline_provenance_curated());
+		expect(document.querySelector('[data-testid="event-edit"]')?.getAttribute('href')).toBe(
+			'/zeitstrahl/events/e1/edit'
+		);
+	});
+
+	it('shows no edit affordance in the header when canWrite is false', () => {
+		const event = makeEntry({
+			kind: 'EVENT',
+			type: 'PERSONAL',
+			derived: false,
+			eventId: 'e1',
+			title: 'X',
+			senderName: '',
+			receiverName: '',
+			documentId: undefined
+		});
+		const bucket: Bucket = {
+			key: 'event:e1',
+			kind: 'event',
+			title: 'X',
+			color: null,
+			letters: [makeEntry({ documentId: 'a' })]
+		};
+		render(LetterBucket, { bucket, mode: 'event', year: 1916, event, canWrite: false });
+		expect(document.querySelector('[data-testid="event-edit"]')).toBeNull();
+	});
+});

frontend/src/lib/timeline/YearBand.svelte

@@ -41,6 +41,7 @@ let {
 
 type Row =
 	| { t: 'event'; entry: TimelineEntryDTO }
+	| { t: 'eventcard'; entry: TimelineEntryDTO; bucket: LetterBucketModel }
 	| { t: 'letter'; entry: TimelineEntryDTO; side: 'left' | 'right' }
 	| { t: 'strip' }
 	| { t: 'bucket'; bucket: LetterBucketModel; nested: boolean };
@@ -52,26 +53,30 @@ const bucketMode = $derived(groupingMode === 'thema' ? 'thema' : 'event');
 const rows = $derived.by<Row[]>(() => {
 	const out: Row[] = [];
 
-	// Ereignis: events stay on the axis (REQ-001); each curated event's letters nest directly
+	// Ereignis: events stay on the axis (REQ-001). A curated event WITH letters in this band
-	// beneath its pill — the pill IS the header, so the title is never repeated. A cluster whose
+	// becomes the contained card's header (no separate pill — its title reads once, #827
-	// pill lives in another year band (or was filtered out) keeps its own header here, and the
+	// redesign); a letterless/derived/world event stays a plain pill/band. A cluster whose event
-	// unlinked letters fall to the single "Weitere Briefe" bucket (REQ-003/006/019).
+	// lives in another year band (or was filtered out) renders as a text-header card here, and
+	// the unlinked letters fall to the single "Weitere Briefe" drawer (REQ-003/006/019).
 	if (groupingMode === 'event') {
 		const buckets = bucketLetters(letters, 'event', eventLookup);
-		const hasPill = (bucketKey: string) =>
+		const sameYearBucket = (id: string | undefined) =>
-			year.entries.some((e) => e.kind === 'EVENT' && `event:${e.eventId}` === bucketKey);
+			id ? buckets.find((b) => b.kind === 'event' && b.key === `event:${id}`) : undefined;
-		// Each pill renders, then its same-year cluster nests directly beneath it (no header).
 		for (const entry of year.entries) {
 			if (entry.kind !== 'EVENT') continue;
-			out.push({ t: 'event', entry });
+			const bucket = sameYearBucket(entry.eventId);
-			const bucket = entry.eventId
+			// A curated event with same-year letters becomes the card header (card replaces pill);
-				? buckets.find((b) => b.kind === 'event' && b.key === `event:${entry.eventId}`)
+			// otherwise it stays a plain pill/world-band.
-				: undefined;
+			if (bucket) out.push({ t: 'eventcard', entry, bucket });
-			if (bucket) out.push({ t: 'bucket', bucket, nested: true });
+			else out.push({ t: 'event', entry });
 		}
-		// Clusters whose pill is in another band keep their header; then the fallback, last.
+		// Cross-year clusters (no matching event entry in this band) and the fallback drawer
+		// render after the axis entries, with their own text header.
 		for (const bucket of buckets) {
-			if (bucket.kind === 'fallback' || !hasPill(bucket.key)) {
+			if (
+				bucket.kind === 'fallback' ||
+				!year.entries.some((e) => e.kind === 'EVENT' && `event:${e.eventId}` === bucket.key)
+			) {
 				out.push({ t: 'bucket', bucket, nested: false });
 			}
 		}
@@ -131,6 +136,14 @@ function rowKey(row: Row): string {
 				{:else}
 					<EventPill entry={row.entry} canWrite={canWrite} />
 				{/if}
+			{:else if row.t === 'eventcard'}
+				<LetterBucket
+					bucket={row.bucket}
+					mode="event"
+					year={year.year}
+					event={row.entry}
+					canWrite={canWrite}
+				/>
 			{:else if row.t === 'letter'}
 				<div class="letter-row" data-side={row.side}>
 					<span data-testid="letter-dot" class="letter-dot bg-surface" aria-hidden="true"></span>

frontend/src/lib/timeline/YearBand.svelte.spec.ts

@@ -222,7 +222,7 @@ describe('YearBand — grouping modes (#827)', () => {
 		expect(chip?.textContent).toContain('Krieg');
 	});
 
-	it('nests an event cluster under its pill in the same year without repeating the title (#827)', () => {
+	it('renders a same-year curated event as one card header, with no separate pill and no duplicate title (#827)', () => {
 		const pill = makeEntry({
 			kind: 'EVENT',
 			type: 'PERSONAL',
@@ -238,14 +238,15 @@ describe('YearBand — grouping modes (#827)', () => {
 		render(YearBand, {
 			year: makeYear(1916, [pill, letter]),
 			groupingMode: 'event',
-			eventLookup: new Map([['e1', 'Ein gewaltiger Stadtbrand']])
+			eventLookup: new Map([['e1', 'Ein gewaltiger Stadtbrand']]),
+			canWrite: true
 		});
-		// the title appears exactly once — on the axis pill, NOT also as a bucket header
+		// the title appears exactly once — in the card header, not also as a separate pill
 		const occurrences =
 			(document.body.textContent ?? '').split('Ein gewaltiger Stadtbrand').length - 1;
 		expect(occurrences).toBe(1);
-		// the letter is still clustered (nested under the pill) as the event-letter card
+		// the event renders as the card header, with its letter clustered inside
-		expect(document.querySelector('[data-testid="letter-bucket"]')).not.toBeNull();
+		expect(document.querySelector('[data-testid="bucket-event-header"]')).not.toBeNull();
 		expect(document.querySelector('a.lcard.ev')).not.toBeNull();
 	});
 

frontend/src/lib/timeline/grouping-event-layer-identity.svelte.spec.ts

@@ -46,13 +46,18 @@ function eventLayerSignature(): string {
 	});
 }
 
+// Brief A links to the curated event p1 (Hochzeit), not the world band — so the world band
+// stays letterless and renders as a plain band in every mode (REQ-001). Under the #827 redesign
+// a curated event WITH letters becomes its cluster card's header, so the signature tracks the
+// stable layer: the letterless world band's marker count and the two titles, which all survive
+// regardless of whether Hochzeit renders as a pill (Datum) or a card header (grouped).
 const mixed = () =>
 	makeTimelineDTO({
 		years: [
 			makeYear(1915, [
 				worldBand('Erster Weltkrieg'),
 				eventPill('Hochzeit'),
-				makeEntry({ documentId: 'a', title: 'Brief A', linkedEventId: 'h1' }),
+				makeEntry({ documentId: 'a', title: 'Brief A', linkedEventId: 'p1' }),
 				makeEntry({
 					documentId: 'b',
 					title: 'Brief B',