- ChatWindow: follow the streaming bubble on every chunk (scrollIntoView block:end),
driven by followStreamRef (true by default, only genuine scroll gestures flip it)
- Remove the agentRunning spacer that pushed content above the viewport at the bottom
- Move the scroll-to-bottom button into the input row (ChatInput scrollToBottomButton slot),
always visible, dimmed at the bottom; click jumps to the live stream or the end
- useAgentSession: drop window pointerdown as scroll-intent marker (send-click was
misread as a scroll-away, disabling follow before the stream started); expose
atBottom/followStreamRef/scrollToBottom
- i18n: add chat.scrollToBottom (en/zh-CN)
luckyyzh