This release rebuilds ShogiArena around a clarified public surface and a new bounded-context internal architecture.

- Reorganized the Python package into `contexts`, `interfaces`, `platform`, and `shared` layers under `_core/`.
- Formalized the public API around `shogiarena.engine`, `shogiarena.tournament`, `shogiarena.cli`, and `shogiarena.composition`.
- Reworked the CLI, dashboard runtime, and tournament orchestration for the 0.3.x line.
- Refreshed packaging metadata and release assets for the public repository and PyPI publication.
