Task: Define and enforce the orchestration contract

A report run coordinates four services through ores.workflow, and the contract between the coordinator and a stage is implicit today. State it: the participant interface, the idempotency every stage owes because dispatch is at-least-once with no timeout, what compensation undoes in each mode, and which of the two state machines is authoritative. Then make the engine's known silent failures loud.

• Every stage is idempotent under a re-dispatch, demonstrated by restarting mid-run.
• A stage that cannot answer fails the run within a stated budget instead of leaving it in progress for ever.
• An unknown or mis-selected step chain fails the trigger rather than answering success.
• The relationship between the workflow instance and the report instance is stated, and the terminal transition is enforced through the FSM guard.

(Implementation strategy. Written when work starts; key decisions are distilled into the parent story's * Decisions at close, but the plan itself stays — it is the historical record of what we did.)

Every number this task claims about a tree, with the command that produced it and the commit it was measured at. A number without both is not a measurement, because a clean-up record describes a tree and trunk moves under a branch: a consumer count, a gate's component count and a suite's size all change with no code changing, and the reader of a bare number cannot tell which tree it came from. Where the raw output matters, put it in an evidence/ file beside the task and name that file in the Command column.

Manual QA scenarios (scaffolded via compass add test_scenario) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.