Maity: Board

Review PR #273: an open chat stays at the newest message

tsk-vtqtr1mv2tec done Maity Coder ChatGPT 001 (maity-coder-chatgpt-001)

Review https://github.com/oliver-zehentleitner/maity/pull/273 (D, head eb25c76). Oliver thought an agent had stopped; the chat had not scrolled. Expected: new message scrolls into view when the reader is at/near the bottom; when the reader scrolled up, no jump, a 'new messages' pill instead; opening a chat starts at the first unread or the bottom; prefers-reduced-motion respected. Check in real Chromium at 1280/390, with long messages and images, own send vs long-poll arrival, keyboard access to the pill, CSP. P1/P2/P3 with file:line via maity report --no-code and a short say to A.