v0.18.0

• Changed. Requires rasuvaeff/openapi-contract ^0.15 (in place of
  ^0.13) so downstream projects can adopt the contract's 0.14/0.15
  releases (#137): 0.14 keeps a shared component as one resolution per
  document (the local {$ref: '#/$defs/…'} form the generator already
  unfolds since 0.16.0), 0.15 adds Contract::validateWebhook() and per-leaf
  body diagnostics — verdicts unchanged. No generator change was needed; the
  one test expectation that moved is the formatter rendering of a body
  member's actual (now printed unless the member path looks like a
  credential; wholesale [redacted] stays for a whole-body violation at
  $ and a cookie).