Disable cytoscape node grabbing so taps fire reliably

Disable cytoscape node grabbing so taps fire reliably

By default cytoscape lets the user drag nodes around. The drag
detector kicks in if the pointer moves more than a few pixels
between mousedown and mouseup, and when that happens cytoscape
suppresses the corresponding 'tap' event — which is what our
hand-rolled double-click handler listens to. So a slightly-jittery
double-click on a class node looked like the node was being dragged
without ever drilling into the instance view.

Set autoungrabify: true at init. Dagre re-runs the layout every time
loadGraph is invoked, so user repositioning of individual nodes was
already throwaway — disabling grabbing is a clean improvement on
both axes.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>