Evidence-tier publishing: ship the best available artifact at all times, with its failures recorded in the manifest (dense first)

The gap (owner question, 2026-07-22): "shouldn't we publish the best version we have available at all times?"

Today there are exactly two publication states: certified default (all gates green, latest.json, pe.py manifest) and nothing. Build N dense completed the first full dense battery since Build J — the best full-pool national artifact that has ever existed — and it lives only on a local disk, because rc=1 means no release manifest and the publish contract requires one. Zero dense tags exist on policyengine/populace-us (20 tags checked 2026-07-22; the nearest artifact is buildl-acs-local, a different product — local-area ACS expansion).

The owner's instinct is right: best-available should be publishable at all times. The wrong implementation would be bypassing gates (that spends the meaning of "published" — the #492 doctrine and today's entire register-alignment arc exist to prevent exactly that). The right implementation is a declared evidence tier, generalizing the #490 pattern (adjudicate, record, ship with the caveat carried in the artifact):

1. An evidence-release contract in populace-data (sibling of validate_release_dir, not a relaxation of it): requires the same required files PLUS a mandatory known_failures block in the release manifest — every gate failure the run recorded, verbatim, with owners (e.g. dense: the Table 1.4 CG row at −30.2% under the 5× stretch bound, owner #487; the 7-column dense tail set with measured shares, owner #481/#487). An evidence release with an EMPTY known_failures block is invalid — the tier exists to carry failures honestly, not to hide them.
2. Builder support: --evidence-release writes the manifest with the known_failures block populated from the actual gate results instead of refusing to export. NOT a bypass flag on the certified path: the certified path is untouched; this is a different output contract, and the artifact name carries the tier (…-evidence-…).
3. Publish mechanics: immutable tag as usual, NEVER latest.json, never the pe.py bundle. A separate latest-evidence.json pointer is allowed so consumers can discover the best current evidence artifact.
4. Supersession: "best available at all times" means best CURRENT — each new evidence publish supersedes the last (Build O dense, running now, would be the first published artifact of this tier rather than N dense).

Non-goals: no change to certified gating; no gate-bypass flags on the certified path; evidence artifacts never feed pe.py certification.

Start with the populace-data validate_release_dir contract and the builder's certified export path described in the issue. Trace how actual gate results become the release manifest, then define the separate evidence-release contract and publication pointers without changing certified outputs. Done means evidence artifacts carry non-empty known_failures, use immutable tags and latest-evidence.json, and never update latest.json or the pe.py bundle.