Motus.NET 0.13.0

Added

• N-leg Walk stack: LeggedMechanism / LegDefinition, GaitSchedule (Song–Waldron duty factor β + phase offsets), ILegIkSolver (LegIk3RSolver, NumericalLegIkSolver seed-only), IBodyPoseSolver (PathFollowBodyPose, TerrainSupportBodyPose with session factory)
• LeggedGait.TryBuild(LeggedMechanism, IBodyPoseSolver?, …) — DriverOffsets packing, IK-fail legs excluded from support, degenerate SSM counted
• LeggedMechanism.ValidateAndCalibrate — assemble + FK↔IK residual gate before Walk
• GaitSchedule.Auto — G = max(2, ⌈N/(N−3)⌉); hex tripod [[0,2,4],[1,3,5]]; N=4 crawl; N≤3 rejected unless AllowDynamicGait
• LeggedLayout.ToMechanism() adapter; HexMithi/QuadSmoke remain NET factories (QuadSmoke sets AllowDynamicGait)

Changed

• HexMithi swing groups corrected from degenerate [[1,3,4],[0,2,5]] to alternating tripod [[0,2,4],[1,3,5]]
• LeggedMethodRefs.DescribeStack / docs/METHODS.md document GaitSchedule and mechanism Walk