v0.4.0

Added

• Map + render library surface — the crate now re-exports the tree model and renderer at
  the crate root, so a downstream consumer can assemble a CodebaseMap from DirNode /
  FileNode by hand (the charter / deps / symbols / warnings fields may be None /
  Vec::new()) and render it via for_format(Format, ascii) + the Renderer trait, driving
  its own tree without the internal build pipeline. Access-only: no behavior or schema change.
  The node field types (Charter, DirDeps, InternalDep, Warning, Symbol, SymbolKind)
  are re-exported too so every field is nameable; the graph/symbols/strict builder machinery
  stays crate-internal.