v0.5.0-preview.1

Breaking

• Options are immutable after construction. GridOptions, VoxelOptions and PathOptions properties are init-only like NavSettings, CrowdOptions and GraphOptions already were, so a shared preset (GridOptions.Default, the defaults used when you pass null) cannot be changed by one caller under another. Code that assigned a property after construction (o.Algorithm = GridAlgorithm.Jps;) must set it in an object initializer (new GridOptions { Algorithm = GridAlgorithm.Jps }). Binary-incompatible with 0.4.0-preview.3 (setters are replaced by init accessors); recompiling is enough. Clone() is kept.
• FindPath gains a trailing CancellationToken cancellationToken = default on Grid, HexGrid, VoxelGrid, NavMesh, NavWorld, NavMeshQuery and the TiledNavMesh extension, so existing source compiles unchanged but already-built callers must be recompiled (the old signatures are gone).

Added

• Cancellation on every tier-1 FindPath: the token is checked every 256 iterations; cancelling throws OperationCanceledException and leaves the grid or mesh untouched. A token that is never cancelled returns exactly the result of no token (slicing never changes a search).
• NavMesh.FindPathAsync and Grid.FindPathAsync (cells and world points): same results as the synchronous forms. The mesh form is NavMeshQuery.FindPathAsync (slices of expansions with a yield between them); the grid form runs the synchronous search on the thread pool.
• Documentation of the cross-tier conventions (immutable options, cancellation, observer-style listeners) in docs/README.md; the 3D builder and mesh format public members got a documentation pass.
• GridSearch runs JPS and JPS+: Grid.CreateSearch accepts GridAlgorithm.Jps and GridAlgorithm.JpsPlus on the engines FindPath uses (the specialised octile jump point search, the generic block-map and JPS+ table searches, or plain A* where FindPath falls back to it), so a budgeted jump point search resumes with Step(budget), returns cell for cell the path and cost bits FindPath returns for every slicing, and saves and restores byte-exactly. One iteration is one pop of a jump point. State kind 12 gains mode 3 (specialised jump point engine), documented in docs/grids-state.md; existing states are unchanged.

Changed

• GridSearch.SaveState(Span<byte>), GetStateSize and RestoreState allocate nothing in steady state on the generic engine too (the handle keeps one serialisation buffer); GridSearch.UsesSpecializedEngine now answers from the options and the grid before the first search.