v0.2.3 — Shared code style

Source, tests and templates now follow the shared NAF code style, and a style workflow keeps
them there. The formatter is a development dependency and does not reach anything you install.

No behaviour changes. The API, the configuration and the dependency constraints are the
same as in v0.2.2; upgrading needs no action.

The README also drops its code-style section. It repeated what this package's AGENTS.md
already says, and contributor guidance belongs there rather than in a file that ships inside
the Composer package. What remains is the introduction, the link to the documentation, the
install command and the licence — the same shape every package in the collection now has.

Validation: the tagged commit passed CI, and its tree passed the suite with 204 tests, 406 assertions.