Round out the canvas editing experience.
- Dragging one card of a multi-selection now moves and persists the whole
selection (React Flow hands the full dragged set to onNodeDragStop).
- A category band is draggable by its header, which moves every technology in
that band; the band body stays click-through.
- A "Snap: On/Off" toolbar toggle (default on, remembered per browser) snaps
dragged cards to a 46px grid that divides the column and row steps, so
snapped cards line up with the automatic layout.
- Connection lines are adjustable: select an edge to reveal "+" handles at each
segment's midpoint (click to add a bend), drag bends to reroute, and
double-click a bend to remove it. Routes persist per browser.
- Edges route around technologies they are not connected to, and corners are
rounded, so lines no longer cut through unrelated cards.
- Ctrl/Cmd-clicking to multi-select no longer pops the side panel over the
canvas.