Root cause: when MessageComplete fires, the reducer atomically moves the
streaming message to the messages list and clears streamingMessage. The
messages list's typing effect condition (lastAnimatedMessageId check)
didn't account for the fact that this message was already rendered with
a typing effect in the streaming slot. The animation replayed from
scratch on the already-complete message, causing a visible blink.
Fix: add message.isStreaming to the condition. Messages finalized via
MessageComplete/MessageDone always have isStreaming=false, so they skip
the replay naturally. The streaming slot's StreamingBubbleWithTypingEffect
continues to handle the animation during active streaming.
Closes#374
Co-authored-by: M57 <hy4ri@users.noreply.github.com>
