Publish Ledger target profile artifacts for Populace builds

[MaxGhenis]

Populace needs a stable Ledger artifact that can be consumed without copying target values into country content.

Need:

• Target profile rows generated from Ledger facts and source packages.
• Structured selectors for source, geography, entity, measure, dimensions, source period, and base-year/uprating policy.
• Measurement bindings for the microsimulation runtime and future rule-engine bindings when available.
• Profile versioning and source coverage diagnostics.

Acceptance criteria:

• A generated artifact exposes target profile rows and consumer facts with a stable schema version.
• Every value resolves from Ledger data and records source provenance.
• Populace can construct a TargetRegistry from the artifact without direct database queries or copied country target values.
• Historical source years remain available, and latest-not-after-base-year selection is explicit in profile metadata.