refactor(personFormat): replace getInitials(Person) with getInitials(name: string)

Unify the initials-extraction logic: the new string-based getInitials()
splits on whitespace, takes the first char of the first and last word
uppercased — matching the pattern that was already inlined in
CommentThread. Update PersonChip, DocumentMetadataDrawer, and
CommentThread to use the shared function.

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

frontend/src/lib/components/DocumentMetadataDrawer.svelte

@@ -2,7 +2,7 @@
 import { m } from '$lib/paraglide/messages.js';
 import { formatDate } from '$lib/utils/date';
 import { formatDocumentStatus } from '$lib/utils/documentStatusLabel';
-import { getInitials as calcInitials, personAvatarColor } from '$lib/utils/personFormat';
+import { getInitials, personAvatarColor } from '$lib/utils/personFormat';
 
 type Person = { id: string; firstName?: string | null; lastName: string; displayName: string };
 type Tag = { id: string; name: string };
@@ -32,10 +32,6 @@ let showAllReceivers = $state(false);
 
 const displayedReceivers = $derived(showAllReceivers ? receivers : visibleReceivers);
 
-function getInitials(person: Person): string {
-	return calcInitials(person);
-}
-
 function getFullName(person: Person): string {
 	return person.displayName;
 }
@@ -51,7 +47,7 @@ function getFullName(person: Person): string {
 			style="background-color: {personAvatarColor(person.id)}"
 			aria-hidden="true"
 		>
-			{getInitials(person)}
+			{getInitials(person.displayName)}
 		</span>
 		<span class="font-serif text-sm text-ink">{getFullName(person)}</span>
 	</a>