v0.18.4

Added

• Added conservative blocked dependency auto-recovery. When a daemon is idle
  with queued same-lineage execution work stranded behind a blocked predecessor,
  it can requeue the predecessor only if blocked metadata classifies the latest
  failure as network_unavailable, provider_unavailable,
  provider_rate_limited, or runner_timeout and cooldown/retry-budget gates
  pass.
• Added millrace queue retry-blocked <TASK_ID> --reason "..." as an audited
  manual blocked-task recovery command, with --root-spec-id and explicit
  --force override support.

Changed

• Runner normalization now records blocked recovery metadata such as
  blocked_origin, failure_scope, auto_requeue_candidate, and a classifier
  code on failure envelopes.