Register raw microdata releases as source artifacts: licence/access manifest fields, hash-only registration, first registrations

[MaxGhenis]

Implements the raw-microdata identity ADR (docs/adr-chronicle-raw-microdata-identity.md, PR opened alongside this issue): Chronicle registers every raw microdata release its consumers build from, stores bytes only for redistributable public-use files, and never parses microdata into rows or facts.

Why now

• Microcosm's raw inputs are pinned in four different places with no shared registry, licence record, or witnessed fetch time: per-country source_stages.json (UK: 19 licensed_microdata + 2 private_microdata entries carry sha256; US: 8 of 37 public_microdata entries carry sha256, 29 do not; BE: the restricted_microdata entry carries none), the ASEC raw-stage checkpoint metadata, code constants (e.g. weeks_unemployed.py), and build_us_multispine_pool.py --*-sha256 arguments. None references a Chronicle artifact.
• Publishers revise and withdraw microdata (IRS PUF withdrawn 2026; Census reissues under the same vintage label). A registered hash with a witnessed fetch time is the only durable statement that a release existed with those bytes.
• The node-graph rebuild (microcosm#836) declares identity per node; the roots of the graph should resolve to one witnessed registration.

Tasks

• Manifest schema: add licence (publisher terms id or URL) and access (public | licensed | restricted, closed set) to manifest.yaml; validate in validate-package / artifact inventory. Today 1 of 159 manifests carries a license field.
• Hash-only registration: fetch-artifact / publish-raw (or a sibling register-artifact) must accept a licensed/restricted entry with checksum, size, vintage, access route and refuse bytes; public entries archive bytes under raw/{source_id}/{package_id}/{year}/{sha256}/{filename} as today.
• Registration is manifest-level: confirm no harness gate demands parsed source rows/cells for a microdata package, or add the explicit carve-out.
• First registrations, from Microcosm's manifests: US public-use files (CPS ASEC pooled vintages, CPS basic monthly 2024, ACS PUMS household/person, SCF 2022, SIPP 2023) with bytes; IRS PUF 2015, FRS 2023-24 tabs, SPI donor, BE-SILC 2023 hash-only. Exact list = every *_microdata artifact kind in packages/microcosm-build/src/microcosm/build/*/source_stages.json.
• Docs: storage-architecture "Object Key Conventions" example for a microdata release; harness doc section on hash-only entries.
• Consumer side: PolicyEngine/microcosm issue (linked below) adds chronicle_artifact references and sha256 to every microdata artifact entry and fails closed on mismatch.

Boundary

Unchanged in substance: no reconciliation, aging, imputation, target activation, or microdata-derived facts. The June 30 removal (#68) of microdata parsers, adapters, and tracked raw storage stands; this adds manifests and two manifest fields only. Licensed bytes never enter a Chronicle store or credential scope.

Related: #143 (ledger→chronicle surface migration; the ledger-raw bucket name is migrating under mechanism 3, registrations should target whichever bucket is current at landing time), microcosm#530 (pin raw PUF), microcosm#665 (UK raw ingest, workstream E), microcosm#204.

[MaxGhenis]

ADR PR: #222