GeoJSON rounding precision inconsistent between draw and editing

* Click rectangle tool
* Draw box
* Note GeoJSON using 15 decimal places
* Drag the feature with space+drag
* Still 15 dp
* Drag corners to resize
* Rounded to 7 dp

* All operations should round to the same precision (of which I agree that 7 dp is a good choice).
* Point / LineString / Polygon rounds to 7dp when drawing and editing
* Circle rounds to 15dp on drawing and editing

Reproduce the rectangle tool flow: draw a box, move it with space+drag, and resize it by dragging corners, then compare the GeoJSON coordinate precision. Trace the drawing and editing paths that serialize Point, LineString, Polygon, and Circle geometries; done means the stated geometries consistently use 7 or 15 decimal places in both drawing and editing.

Written by the indexing model from the issue text.