v0.8.0

• Breaking. RequestMaterializer, RequestCaseArbitrary and
  ResponseCaseArbitrary no longer accept their @internal collaborators as
  constructor parameters (#53). Every one had a default and nothing in the
  package, its tests, its examples or its documentation ever passed one, so no
  documented usage changes — but the signature published a type the package
  does not support overriding. RequestMaterializer keeps $baseUri, now its
  third parameter; withBaseUri() is the documented way to set it either way.
• SecuritySelector is @api. It was marked @internal while the README
  showed a snippet constructing it to materialize a request outside a suite;
  the snippet is the contract, and the class only ever exposed public types.
• The seven parameter misuse categories of NegativeRequestCaseArbitrary no
  longer restate the path/query/header/cookie handling and the full case shape
  once each: one parameter() helper writes the target's value through a
  single location map, and one imported psalm type describes the case. A
  location can now be mishandled in exactly one place.
• Helpers that were carried verbatim in several classes are shared:
  MediaType (normalization and the JSON test, nine call sites),
  SchemaShape (array/object schema, three copies), WireValue (the scalar
  wire spelling, four copies with four different failure wordings), and
  ConstructibleCategories (drop the misuse categories a document does not
  admit, then choose uniformly — two copies).
• ResponseCaseArbitrary discovers the JSON media type of a response once
  instead of once per caller; each caller still words its own "no JSON media
  type" failure.
• Removed a re-check of is_string() in ContainerArbitraries that the loop
  above already enforced, and the single-use withValue() wrapper in
  RequestMaterializer.
• README (EN/RU) carries the sections the package conventions require:
  Requirements, Examples, Development and License, plus the llms.txt pointer
  and a Psalm-level badge.
• examples/README.md lists the scripts as a table and says how to run them.