caugi 1.1.0

New Features

• Add normalize_latent_structure(), which normalizes the latent structure of a
  DAG while preserving the marginal model over observed variables.
• Add minimal_d_separator(), which computes a minimal d-separator between
  sets of nodes in a DAG, with support for mandatory inclusions and restrictions.
• Add posteriors() query function, which is the dual of anteriors(). It
  returns all nodes reachable by following paths where every edge is either
  undirected or directed away from the source node. For DAGs, posteriors()
  equals descendants(). For PDAGs and AGs, it includes both descendants and
  nodes reachable via undirected edges.
• You can now specify whether to use an open or closed graph definition for the
  queries ancestors(), anteriors(), descendants(), and posteriors().
  This can be set globally with caugi_options() or locally with the
  open = TRUE/FALSE argument. The default remains open = TRUE.
• Add is_mpdag() query to check whether a PDAG is closed under Meek's
  orientation rules (R1-R4), and meek_closure() to orient all implied edges
  until Meek closure.

Improvements

• caugi_options() now supports nested key drilling: multiple unnamed arguments
  traverse nested options (e.g., caugi_options("plot", "tier_style", "fill")).
• Rust remains the single source of truth for graph state. Graph properties
  (simple, graph_class, nodes, edges) are sourced from the session.
  • A session is always created, including empty graphs (n = 0), which simplifies
    property access.
  • Deprecated compatibility properties @.state, @name_index_map, @built,
    and @ptr now warn on access and return NULL.
  • Deprecated compatibility constructor arguments build and state in
    caugi() now warn and are ignored.
• The inplace parameter in verb functions (add_edges(), remove_edges(),
  set_edges(), add_nodes(), remove_nodes()). All graph modifications now use
  copy-on-write semantics for consistency with R conventions. The parameter is
  deprecated and ignored with a warning.
• Added all.equal and compare_proxy methods for caugi objects to support
  graph-content comparison in tests.
• Add asp parameter to plot() for controlling the aspect ratio. When asp = 1,
  the plot respects equal units on both axes, preserving the layout
  coordinates. Works like base R's asp parameter (y/x aspect ratio) (#195).
• Add pdag_to_dag() function that generates a random DAG consistent with a
  given CPDAG/PDAG structure if possible (#201).

Bug Fixes

• Fixed a bug causing plot() to use incorrect layout if node names were not
  in the same order as in the graph object (#198).
• Fixed set_edges() so that it correctly replaces symmetric edges in
  simple graphs.

Deprecations

• The parameter all in districts() has been deprecated. Use districts()
  without arguments to get all districts.