The planning chart keeps up when you scroll it

Scrolling the planning chart sideways is smooth now, and the dates header no longer lags behind the bars underneath it.

The header used to be redrawn in step with the scroll, one frame late, so it visibly slid out of alignment with the columns it labels and was worst while more of the plan was loading. It is now pinned to the scroll position directly, so the two move as one thing.

Dragging the divider between the table and the chart, and drawing a selection box across bars, are no longer slow either.