feat(timeline): add compact + event variants to LetterCard

The event variant adds the .lcard.ev marker for letters living inside a
contained event card; the compact variant tightens the row (py-1, text-xs
title) and drops the redundant date chip when the title already embeds the
date. suppressTagChip lets a caller that already conveys the topic hide the
per-letter root-tag chip. Plain Datum letters are unchanged.

Refs #850

frontend/src/lib/timeline/LetterCard.svelte

@@ -11,11 +11,31 @@ type TimelineEntryDTO = components['schemas']['TimelineEntryDTO'];
  * A single archive letter on the timeline: sender → receiver, title, and a
  * precision-aware date chip, linking to the document. Names/titles are
  * OCR/import-derived — rendered via default `{...}` escaping with
- * `whitespace-pre-line` for line breaks (REQ-021); never the raw-HTML directive.
+ * `whitespace-pre-line` for line breaks (REQ-010); never the raw-HTML directive.
+ *
+ * Inside an event cluster the card sits in the contained event card and renders as
+ * the `.lcard.ev` `compact` variant (#850, REQ-002): tighter row, and the redundant
+ * date chip is dropped when the title already embeds the date. The per-letter tag
+ * chip can be suppressed via `suppressTagChip` for callers that already convey it.
  */
-let { entry }: { entry: TimelineEntryDTO } = $props();
+let {
+	entry,
+	variant = 'plain',
+	suppressTagChip = false,
+	compact = false
+}: {
+	entry: TimelineEntryDTO;
+	variant?: 'plain' | 'event';
+	suppressTagChip?: boolean;
+	compact?: boolean;
+} = $props();
 
+const isEventVariant = $derived(variant === 'event');
 const dateLabel = $derived(timelineDateLabel(entry.eventDate, entry.precision, entry.eventDateEnd));
+// Inside an event card the year frames the time, and these archive titles already
+// embed the date — so the compact in-card letter drops the redundant date chip when a
+// title is present, halving the row height and killing the duplicate date (#850).
+const showDate = $derived(!compact || !entry.title);
 const sender = $derived(entry.senderName === '' ? m.timeline_unknown_person() : entry.senderName);
 const receiver = $derived(
 	entry.receiverName === '' ? m.timeline_unknown_person() : entry.receiverName
@@ -28,28 +48,37 @@ const receiver = $derived(
 <a
 	href="/documents/{entry.documentId}"
 	style="display: flex; flex-direction: column; justify-content: center; min-height: 44px"
-	class="rounded-sm border border-l-[3px] border-line border-l-brand-mint bg-surface px-3 py-2 shadow-sm transition-colors hover:border-brand-mint focus:outline-none focus-visible:ring-2 focus-visible:ring-brand-navy"
+	class="lcard rounded-sm border border-l-[3px] border-line border-l-brand-mint bg-surface px-3 shadow-sm transition-colors hover:border-brand-mint focus:outline-none focus-visible:ring-2 focus-visible:ring-brand-navy"
+	class:py-2={!compact}
+	class:py-1={compact}
+	class:ev={isEventVariant}
+	class:compact={compact}
 >
 	{#if entry.title}
 		<!-- ✉ + sr-only label are static chrome rendered as sibling nodes, NEVER
 		     interpolated into the escaped user title; the title keeps its own
 		     pre-line span for multi-line OCR text (REQ-008/016/021). -->
-		<span class="font-serif text-sm font-bold break-words text-ink">
+		<span
+			class="font-serif font-bold break-words text-ink"
+			class:text-sm={!compact}
+			class:text-xs={compact}
+		>
 			<GlyphLabel glyph="✉" label={m.timeline_letter_glyph_label()} />
 			<span class="whitespace-pre-line">{entry.title}</span>
 		</span>
 	{/if}
-	<span class="mt-0.5 font-sans text-xs break-words text-ink-3">
+	<span class="font-sans text-xs break-words text-ink-3" class:mt-0.5={!compact}>
 		<span class="font-serif whitespace-pre-line">{sender}</span>
 		<span aria-hidden="true">→</span>
 		<span class="font-serif whitespace-pre-line">{receiver}</span>
-		{#if dateLabel}
+		{#if dateLabel && showDate}
 			<span data-testid="letter-date"> · {dateLabel}</span>
 		{/if}
 	</span>
-	{#if entry.rootTagName}
+	{#if entry.rootTagName && !suppressTagChip}
 		<!-- The primary root-tag chip sits on its own line beneath the meta line
-		     (#835 §3); absent when the letter has no tag (REQ-005). -->
+		     (#835 §3); absent when the letter has no tag (REQ-006), and suppressed when
+		     the caller already conveys the topic (suppressTagChip). -->
 		<TagChip name={entry.rootTagName} color={entry.rootTagColor ?? null} />
 	{/if}
 </a>

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

@@ -127,3 +127,46 @@ describe('LetterCard', () => {
 		expect(chip?.textContent).toContain('Familie');
 	});
 });
+
+describe('LetterCard — event-cluster variants (#850, REQ-002)', () => {
+	it('carries the .lcard.ev class in the event variant (REQ-002)', () => {
+		render(LetterCard, { entry: makeEntry(), variant: 'event' });
+		expect(document.querySelector('a.lcard.ev')).not.toBeNull();
+	});
+
+	it('is a plain card with no .ev marker by default (REQ-006)', () => {
+		render(LetterCard, { entry: makeEntry() });
+		expect(document.querySelector('a.ev')).toBeNull();
+	});
+
+	it('suppresses the per-letter tag chip when asked, even with a root tag', () => {
+		render(LetterCard, {
+			entry: makeEntry({ rootTagName: 'Krieg', rootTagColor: 'sienna' }),
+			suppressTagChip: true
+		});
+		expect(document.querySelector('[data-testid="tag-chip"]')).toBeNull();
+	});
+
+	it('still shows the per-letter tag chip when not suppressed', () => {
+		render(LetterCard, { entry: makeEntry({ rootTagName: 'Krieg', rootTagColor: 'sienna' }) });
+		expect(document.querySelector('[data-testid="tag-chip"]')).not.toBeNull();
+	});
+
+	it('drops the redundant date line in the compact variant when a title is present (#850)', () => {
+		// Inside an event card the year already frames the time, and these archive titles
+		// embed the date — so the compact in-card letter omits the date chip.
+		render(LetterCard, { entry: makeEntry({ title: 'H-0023 – 6. Juli 1916' }), compact: true });
+		expect(document.querySelector('[data-testid="letter-date"]')).toBeNull();
+		expect(document.body.textContent).toContain('Karl Raddatz'); // sender still shown
+	});
+
+	it('keeps the date in the compact variant when the letter has no title (#850)', () => {
+		render(LetterCard, { entry: makeEntry({ title: undefined }), compact: true });
+		expect(document.querySelector('[data-testid="letter-date"]')).not.toBeNull();
+	});
+
+	it('renders the compact variant on a single tighter row (#850)', () => {
+		render(LetterCard, { entry: makeEntry(), compact: true });
+		expect(document.querySelector('a.lcard.compact')).not.toBeNull();
+	});
+});