Release v4.1.0

Summary

Four fixes to the PivotViewer, all found while using it in the Chronicle Workbench. Long card
text painted over neighbouring cards, the toolbar forced a heading no host asked for, pinch to
zoom silently did nothing, and zooming could leave the viewer showing an empty canvas with no
obvious way back.

Added

• PivotViewer accepts an optional title for the toolbar heading. Omit it and the heading
  collapses entirely, leaving the item count directly beside the filter button.

Changed

• The toolbar heading renders as a span sized by Components rather than a bare h1, so it no
  longer inherits whatever heading size the consuming application had set.
• The toolbar's item count is sized to the filter button beside it, so the two read as one group.

Fixed

• Card titles and value columns are measured and ellipsized to fit the card. Text longer than the
  card previously kept painting past its edge and over the card next to it.
• Pinch to zoom works again on trackpads, and on touch devices the viewport no longer gives the
  two-finger gesture away to the browser. The zoom listeners were bound before the viewport
  existed and never rebound, so the gesture did nothing until the zoom was changed some other way
  first.
• The viewport keeps its place when a zoom change resizes the content. Zooming out far enough
  collapsed the scroll range, and zooming back in left the offset at zero — which in grouped mode,
  where cards are drawn from the bottom up, showed a blank canvas until the user scrolled all the
  way back down.