refactor(document): remove statusLabel() alias, use formatDocumentStatus directly

statusLabel() was a one-line alias for formatDocumentStatus() with no
additional behaviour. Remove it and update DocumentStatusChip.svelte to
call formatDocumentStatus() directly. Remove the corresponding alias
test suite from the spec file.

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

frontend/src/lib/document/documentStatusLabel.ts

@@ -33,7 +33,3 @@ export function statusDotClass(status: DocumentStatus): string {
 			return 'bg-emerald-600';
 	}
 }
-
-export function statusLabel(status: string): string {
-	return formatDocumentStatus(status);
-}