Extract the shared assistant-name predicate (resolveAssistantName: trimmed name or null) used by typing-indicator + message-item, and unit-test the branches (name shown; whitespace-only -> 'AI agent' fallback; undefined -> fallback). Behavior-identical (|| -> ?? since the helper returns null). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>