Adds rolling 20-sample history to KPI struct, an extraDraw overload to TextRasterizer, and CG-path sparklines drawn right-aligned in KPIClusterWidget. Other widgets not modified. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>