Allow free scrolling during text streaming

[benjaminshafii]

Request\nEnsure the UI does not lock scroll position while text is streaming, so users can freely scroll up while streaming continues.\n\n## Why\nLocking scroll prevents users from reviewing earlier content during long responses.\n\n## Acceptance Criteria\n- Streaming updates do not force-scroll the view when the user has scrolled up.\n- Provide a clear way to return to the latest content (e.g., a "Jump to latest" button) if applicable.\n- Works consistently across desktop and mobile layouts.\n