scrollIntoView({ behavior: 'smooth' }) on the thread's nested scroller never
moved it in Chrome — measured live: scrollTop stayed 0 after sending and
after the reply, while the instant form scrolled to the end. A long
conversation therefore showed its oldest messages after every turn, with
the new reply out of view below. Instant it is.
Co-Authored-By: Claude Fable 5 <[email protected]>