Build on top of v1.8.3-beta.1.
- Baseline band below Y=0 now uses the SAME opacity (30 percent) as the production area above, so the band reads as a continuous extension of the area instead of a paler hint of it.
- Cumulative grid import + export curves added to the chart as dashed lines in the HA Energy grid palette: import in --energy-grid-consumption-color, export in --energy-grid-return-color. The per-entity sample buffers (the timeline scrub already uses the same data path) are summed at the union timeline so multi-entity grids work correctly. Past day offsets resolve via the 5-day LTS arm refreshGrid already runs. The chart Y axis auto-expands when a grid curve dwarfs the production curve (winter day with no production + heavy import).