replaced hand-rolled DFS slot algorithm with dagre (Sugiyama-style layered layout). Correct layering for acts-without-scenes, cross-edge handling, cycle detection. Tree edges (parent→child) and explicit edges both feed dagre. _positions map interface unchanged so drawEdges(), drag, and fullscreen all unaffected. nodesep: 32, ranksep: 64, rankdir: TB. ADR-0076. 637 tests green.
BL-089
Shipped