- Introduce `MessageRenderContext` and `MessageCacheEntry` for caching wrapped lines per message.
- Implement `render_message_lines_cached` using cache, invalidating on updates.
- Add role/style helpers and content hashing for cache validation.
- Throttle UI redraws in the main loop during active streaming (50 ms interval) and adjust idle tick timing.
- Update drawing logic to use cached rendering and manage draw intervals.
- Remove unused `role_color` function and adjust imports accordingly.