Release v4.16.2

Changed

• A model whose authorization references an opaque (code) policy still fails with STAGE-ESM-015, and the diagnostic now names what is missing: the policy's implementation attachment is not part of the render request, and Arc has no exact received-at time for PolicyContext.Occurred. Stage never emits a policy with a substituted time or a predicate that silently denies.
• The renderer guide documents that a keyed query's policy subject is the query key, matching Screenplay's reference evaluator.

Fixed

• Stage's in-memory runtime and specification executor report an opaque policy they reach as unsupported instead of allowing or denying it, following authored order: a portable operand that decides first still decides (Screenplay decision 0005).
• An unsupported authorization result is no longer replaced by a contract rejection when the command payload fails to bind.