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>
claude code agent 227