The editor stored the dragged point index as Option<usize> but read it back
as usize, so the index was lost after the first frame: pressing on a point
did nothing and only click-to-add (overwrite) worked. Points now drag in X
and Y (X clamped between the neighbours), picked at the press origin, with a
grab cursor, a highlighted point and an input/output readout; one undo step
per drag via develop.beginInteraction / endInteraction.
Fixes#12
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Brandon ThomasandClaude Opus 5.5
e1acdb876d