GTM API / Resume mass-action

Unfreeze dispatch: status becomes active, paused_reason and hold_till are cleared, and pending items are re-planned onto a fresh jitter chain from now. Items that deferred mid-cascade restart at their current step, so completed steps are not re-run. Does NOT touch the canary gate: after a canary_failed pause only the retried canary dispatches, and release_mass_action_canary is what opens the gate. Resumed before its hold_till, a limit_reached run holds again at the first item the budget refuses. 409 invalid_transition if the run is not paused. Contract: - MCP tool resume_mass_action, registry package mcp.orchestration/mass_actions, mount orchestration.mass_actions. - Operation action, response envelope action. - Flags: none.