0.24.0

Added

• settings: on a component states each configuration input once, with a type drawn
  from the specification's own types:. ess specify runtime compile derives the
  ess-runtime/1 config and secret slots from that declaration — the environment
  variable upper-snake-cased from the setting name, the kind from the setting's type
  and any literal — and refuses a runtime document that hand-authors a slot for a
  component that declares settings, or two declarations that would bind one
  environment variable twice in one container, naming the settings and the components.
  A setting states absence with Optional<…> and with nothing else: a secret typed
  Optional<…>, and a setting typed by a name whose representation is Optional<…>,
  are refused where they are written. The key is optional and serialises out when
  unset, so every document that does not use it compiles to the bytes it always did;
  the source format stays ess/4, and a build older than 0.24.0 refuses a document
  that uses the key, because a component's fields are deny_unknown_fields.
• ess conform run --target interpreted is selectable beside billing and
  oracle-fixture. The target decides nothing yet: every method refuses with
  TargetError::unsupported, so every scenario returns one unsatisfied obligation and
  the run fails rather than errors. It is the seam the model-driven interpretation
  epic fills.
• The ESS toolchain is specified in ESS, under models/toolchain, and its enums are
  gated against the source they describe.

Fixed

• A command name declared twice is refused even when the first of the two declarations
  has an error of its own. Before, a first declaration that failed its own try_from
  never reached the name check, so the second silently took the name and the author
  was told about one error instead of two.
• Every literal a document writes is checked, however deep. A literal inside an
  Optional<…> of a type whose ring is broken is owned by one pass rather than
  falling between two.
• uniqueItems is decided the same way wherever schema-contract validates.
• A refusal about a closed enum names the enum it is about and cites the file that
  holds it.