v0.49.0

Added

• ContractKind::BeatBenchmark (PMAT-741) — the measurement backbone for the
  four-pillar "replace AND beat" mission: a contract kind for committed, CI-wired
  head-to-head BEAT claims (apr ≥ incumbent on a canonical task, pinned baseline,
  fails CI on regression). Ships the pilot contracts/beat-sklearn-iris-v1.yaml.
  Marks the campaign's pivot from sklearn-parity breadth to BEATS-as-CI-artifacts.