Task: Implement Run a full report: scheduling, reporting and compute

One report definition runs end to end from the scheduler through the workflow to the compute grid and back, with a knob that selects which stages run, so demo mode proves the machinery and full mode is the target.

• A definition selects its execution mode, and the stages that mode names are the stages that run.
• Demo mode runs the vendored input tarball through the real grid and retrieves the output.
• Full mode is designed to the same seam, so adding it changes no stage that demo mode already proves.

(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.