## What changed
- Render sparse, fading stars across the composer when using an Astra model in a true-color terminal.
- Preserve composer content, cursor state, effort effects, and terminal colors, and pause the animation while popups are open.
- Add the default-on `tui.whimsy` setting so decorative effects can be disabled independently. Sparkles also respect `tui.animations`.
## Testing
- Cover model and setting eligibility, terminal color handling, protected composer cells, popup behavior, effort effects, and layout stability.
GitOrigin-RevId: fe0471ebef0bca21c44e1d8f731d46959eba0165