feat: intro page, undo/redo, transition fix, naming and stats polish

feat: stable view on pruning toggle, stage-aware stats, route stats panel

feat: room/exit/isolated connectivity, real-time route breaks, broken highlight

feat: hover-select glow, persistent route endpoints, live connectivity

feat: graph-editor UX overhaul and headless matplotlib fix

feat: interactive A*/Dijkstra navigation in the graph viewer

Deploy: floorplan rendered as DOM element, edges always visible