Task: Record the sourcing and curation methodology

(Describe what user-visible-or-internal change this task produces.)

(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.

The methodology is written at How the pricing engine data is sourced and curated. It states six principles, the seven layers and their artefacts, the curation file schema with reason, source, curator and date, the per-row provenance fields, the generator gates and the review a curator follows. It records what the DQ pipeline carries and what it does not: the source commit, the curation version, the coverage counts and the methodology link go on the DQ dataset; the value rules stay in the data model and the write path.

Review addressed two claims that read as present fact: the ORE commit is measured at 3d75a6908 but is not yet recorded on the dataset, and the provenance columns are a target. Both now say so. The curation path is marked as a target, because the directory does not exist yet.

Merged in #3741.