v0.15.4

[0.15.4] - 2026-04-27

0.15.4 adds default-off runtime-owned usage governance so operators can let
Millrace automatically pause between stages when configured token or subscription
quota limits are reached.

Added

• Added [usage_governance] config with runtime token rules, optional
  subscription quota rules, auto-resume behavior, and next-tick apply
  boundaries.
• Added durable usage governance state and ledger artifacts under
  millrace-agents/state/.
• Added runtime-owned pause source tracking so operator pauses and governance
  pauses can coexist without overwriting each other.
• Added status and live daemon monitor output for active usage blockers,
  subscription telemetry degradation, governance pause, and governance resume
  events.

Changed

• Runtime ticks now evaluate usage governance before launching a stage and after
  persisting a stage result, preserving the between-stage execution boundary.
• millrace control resume now clears operator pause intent without bypassing an
  active usage-governance blocker.
• Stage-result token usage can be reconciled back into the governance ledger
  after restart if a ledger write was missing.