Sheprd v0.4.0

Added

• Version factory receipts with explicit timing, attempt counts, acceptance,
  failure stage, review, and authoritative-cost availability fields,
  while retaining schema-1 v0.3.1 receipt compatibility.
• Add read-only sheprd factory stats [project] human and JSON aggregation for
  acceptance, corrections, checks, failures, runtime coverage, and
  authoritative cost only, with strict private-state and stable-read checks.
• Recognize a stable dead-PID factory lock without mutating it while continuing
  to reject live, malformed, unsafe, racing, or unverifiable locks.
• Count trusted receipt-less interrupted runs separately without weakening
  validation for completed receipts or mutating recovery state.