Space when dragging to shift what's being drawn

For anything that can be dragged with the mouse clicked down, Space should offset it while held down. We have this in a few places (like dragging the next preview segment in the Pen tool), but it should be universal across all dragging actions in every tool.

- Select tool:
- [ ] Transform cage resizing, skewing, and rotating
- [ ] Box and lasso area selection
- Artboard tool:
- [ ] Artboard drawing and resizing
- Gradient tool:
- [ ] Gradient line drawing and endpoint moving
- Path tool:
- [ ] Box and lasso area selection
- Line tool:
- [ ] Line drawing and endpoint moving
- Rectangle/Ellipse/Polygon tools:
- [ ] New shape drawing (and resizing after #1715)
- Text tool:
- [ ] Text area drawing and resizing
- And in the node graph:
- [ ] Box (and lasso after #2532) area selection

Start by examining the existing Space behavior when dragging the Pen tool's next preview segment, then trace how dragging is handled in each listed tool. Extend the behavior across the Select, Artboard, Gradient, Path, Line, shape, Text, and node graph actions, and verify that every checklist item offsets the dragged content while Space is held.

Written by the indexing model from the issue text.