What: Feedback (back) edges now alternate between left and right sides
instead of all routing to the right.
Why: Multiple feedback edges targeting the same node (e.g. reviewer→coder
and tester→coder) were overlapping on the right side.
Changes:
- types.ts: add feedbackSide field to ConditionEdgeData
- use-layout.ts: track feedback count per target, alternate sides
- condition-edge.tsx: feedbackPath() accepts side param, mirrors path for left
Ref: #247, closes#249