GTM API / Preview mass-action plan

Validate a bulk plan without running anything and mint the consent token create_mass_action consumes. ALWAYS the first call of a bulk dispatch. One pass, all findings at once: plan shape (1..3 steps), step-eligibility of each tool, scope shape and size (1..100), the generate-scope rule (step 1 must mint an object), the send-class schedule mandate. A tool outside the step vocabulary is 422 with field_errors["plan.steps.{i}.tool"][0].rule = "not_step_eligible". Nothing is persisted, charged or created. Result: preview (items_count, steps_per_item, dangerous_steps, eta, warnings), commit_token, expires_at. eta.starts is when item 1 starts (ISO when scheduled, else asap); eta.estimated_completion_at is starts plus (items_count - 1) mean gaps, null for ASAP or an empty scope. warnings are non-blocking, today one per step arg with an unresolved {{placeholder}} (args go out verbatim). Show the preview, then pass the token to create_mass_action UNCHANGED with the same inputs (an HMAC over them). Tokens live 15 min. Contract: - MCP tool preview_mass_action, registry package mcp.orchestration/mass_actions, mount orchestration.mass_actions. - Operation action, response envelope action. - Flags: read only.