Reasoning ("Thinking") rendered through MarkdownTextContent with a smooth
typewriter reveal. TextMessagePartProvider mints a fresh part object on every
text change, and useSmooth resets its reveal to empty whenever the part
identity changes — so each reasoning delta restarted the animation from the
first character (h / hell / hello wo ...). Token-streaming reasoners
(R1/Qwen/GLM/Claude thinking) fire a delta per token and flash hard; GPT-5's
coarse reasoning summary updates too rarely to notice, which is why it looked
fine.
Drop smooth on the reasoning path so it plain-appends, exactly like the
assistant answer already does. Removes the now-dead smooth plumbing too.
a4c9b069dc