Changes

1. content-visibility: auto on .msg / .tool / .turn-collapse / .process-card

   • Off-screen elements skip paint → layer texture memory drops from ~97 MB to only the visible viewport
   • Paint count no longer grows linearly with session length

2. Remove streaming cursor

   • Remove the blink-animated cursor injected by Markdown.tsx into streaming output
   • Each blink triggered a full document paint — root cause of frequent flicker and high layer memory

Files changed

• desktop/frontend/src/styles.css — content-visibility rules + cursor/blink keyframe cleanup
• desktop/frontend/src/components/Markdown.tsx — removed cursor injection/removal functions, showCursor prop, useLayoutEffect
• desktop/frontend/src/components/Message.tsx — removed showCursor={item.streaming}