Bug

When a user scrolls up in the WebChat UI to read older messages, new incoming messages (including streaming chunks) force-scroll them back to the bottom. This makes it impossible to read conversation history while the agent is responding.

Root Causes

1. Threshold too tight — distanceFromBottom < 200 means a single long message puts you "near bottom" again
2. refreshChat() force-scrolls — calls scheduleChatScroll(host, true) which ignores user scroll position
3. Streaming chunks retrigger scroll — rapid scheduleChatScroll calls during streaming constantly reset position

Expected Behavior

• If the user has deliberately scrolled up (more than ~450px from bottom), new messages should NOT auto-scroll
• A "new messages below" indicator should appear instead
• Auto-scroll should only be forced on initial page load, not during active use
• When user scrolls back to bottom, normal auto-scroll behavior resumes

Proposed Fix

• Increase near-bottom threshold from 200px to 450px (extracted to named constant)
• Make force=true only effective on initial load (!chatHasAutoScrolled)
• Add chatNewMessagesBelow flag for future UI indicator
• Remove force-scroll from refreshChat()

Environment

• OpenClaw 2026.2.1
• macOS WebChat (Brave app mode)