Regrasp Planning 2D: Pose Graph and Pick-and-Place

This 2D companion to the 3D regrasp-planning simulator runs the identical discrete model — six stable "face-up" poses of a cube as graph nodes, with a direct grasp-and-rotate edge only when the required wrist rotation is within the gripper's limit — but fixes a real bug the 3D version's own quaternion math had (see "How this 2D companion differs" below, verified numerically in a scratch script) and renders it as two flat, always-legible views instead of one orbitable 3D scene: a draggable, zoomable pose graph on top showing every reachable hop and the breadth-first-search path highlighted in orange, and a side-view schematic strip below where the gripper physically executes the plan step by step — approach, grasp, lift, rotate, lower, release — with live readouts of the plan length, how many graph nodes the search touched, and the cumulative wrist rotation actually performed. Tighten the wrist-rotation-limit slider below 180° and watch opposite-face reorientations split into a two-hop regrasp through an adjacent pose.