fix(person-mention): truncate notes excerpt at last word boundary

Leonie FINDING-04 + Elicit E5: notes.slice(0, 120) cuts mid-word, especially
ugly in German compound nouns ("…Familienzu…"). Sara #7: the assertion
.toBeLessThanOrEqual(122) was a magic number that hid this bug.

Add truncateAtWordBoundary(text, max): cut at the last space inside the
window unless it'd shrink the excerpt below 70% (single-word fallback).
Single-word case still produces hard-cut + ellipsis so a 150-char word
shows the first 120 chars + … rather than nothing.

Tests pinned to exact strings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/PersonHoverCard.svelte.spec.ts

@@ -197,7 +197,9 @@ describe('PersonHoverCard — loaded state', () => {
 		await expect.element(page.getByText('Born in Berlin.')).toBeInTheDocument();
 	});
 
-	it('truncates notes longer than 120 characters with an ellipsis', async () => {
+	it('truncates notes longer than 120 characters with an ellipsis (single long word)', async () => {
+		// Single 150-char word with no spaces: word-boundary cut would yield nothing,
+		// so fall back to a hard cut at 120 + ellipsis (Sara #7: pin the exact length).
 		const long = 'x'.repeat(150);
 		const withLongNotes = { ...AUGUSTE, notes: long } as Person;
 		render(PersonHoverCard, {
@@ -207,8 +209,34 @@ describe('PersonHoverCard — loaded state', () => {
 			state: { status: 'loaded', person: withLongNotes, relationships: [] }
 		});
 		const notes = document.querySelector('[data-testid="person-hover-card-notes"]')!;
-		expect(notes.textContent!.length).toBeLessThanOrEqual(122);
-		expect(notes.textContent).toContain('…');
+		expect(notes.textContent).toBe('x'.repeat(120) + '…');
+	});
+
+	it('truncates at the last word boundary inside the 120-char window (Leonie FINDING-04)', async () => {
+		// 150-char string with spaces — must cut at the last space, not mid-word.
+		const sentence = 'Sie war eine bekannte Schriftstellerin und engagierte sich '.repeat(3);
+		// length is 180, last space at idx ≤120
+		const withLongNotes = { ...AUGUSTE, notes: sentence } as Person;
+		render(PersonHoverCard, {
+			personId: 'p-aug',
+			cardId: 'card-1',
+			position: POSITION,
+			state: { status: 'loaded', person: withLongNotes, relationships: [] }
+		});
+		const notes = document.querySelector('[data-testid="person-hover-card-notes"]')!;
+		const text = notes.textContent ?? '';
+		// Ends with ellipsis
+		expect(text.endsWith('…')).toBe(true);
+		// Last char before the ellipsis is NOT a half-word — verify by checking that
+		// the position right before … is the end of a word (i.e., there's no letter
+		// further along in the original text immediately after our cut point).
+		const cut = text.slice(0, -1); // strip the …
+		// Find this cut substring in the original sentence
+		const idx = sentence.indexOf(cut);
+		expect(idx).toBe(0);
+		const charAfterCut = sentence[cut.length];
+		// The next char should be a space — confirming we cut on a boundary
+		expect(charAfterCut).toBe(' ');
 	});
 
 	it('omits notes section when notes is null', async () => {