Dragging an edge now rings the port it would connect to and snaps the line
there. A drop on a node's body takes that node's first free compatible port,
or the last compatible one when none is free, replacing its link. A drop into
empty space opens the palette filtered to the node types the edge could reach
at all, and the picked node arrives wired - node and link as one undo step,
so a single undo takes back the whole gesture.
The decision of what fits what lives in core/graph/dropTarget.ts as pure
functions, tested directly; the canvas only draws the answer. The palette
takes an optional filter rather than knowing about drags.
Verified remote on the Windows box (GPU): ALL PASSED, 284 checks.
root
ebad3fd530