Breaking - db v4 schema: 'num_gates' renamed to 'feeders_per_root'; dropped 'valid', 'is_normalized', 'stuntC'. migrate.py accepts v2 and v3. Highlights - OR-Tools MILP backend switched to MathOpt API (unified wrapper). - Pyomo CPLEX/Gurobi switched to persistent interfaces. - PathFinder: 'A' now mandatory; improved heuristics and defaults. - LKH: capacity-violation-triggered iterations; new 'warmstart' arg. - Better pre-optimization estimate of obstructed feeder lengths. - Context-managed database connection API with 'timeout' argument. - CI matrix on Python 3.11-3.14 (default 3.14). Fixes - Numerous PathFinder and make_planar_embedding robustness fixes. - validate_routeset detour-range and touchpoint corrections. - SQLite WAL mode removed (issues on shared clusters). - Stunt vertices no longer placed in G. - migrate.py ImportError fixed.